diff --git a/LocoKit/Base/Timelines/Items/Path.swift b/LocoKit/Base/Timelines/Items/Path.swift
index f7f6a6d8..184ce78d 100644
--- a/LocoKit/Base/Timelines/Items/Path.swift
+++ b/LocoKit/Base/Timelines/Items/Path.swift
@@ -242,8 +242,8 @@ open class Path: TimelineItem {
     }
 
     override open func samplesChanged() {
-        _distance = nil
         super.samplesChanged()
+        _distance = nil
     }
 }
 
diff --git a/LocoKit/Base/Timelines/Merge.swift b/LocoKit/Base/Timelines/Merge.swift
index 3d124a5f..2236209a 100644
--- a/LocoKit/Base/Timelines/Merge.swift
+++ b/LocoKit/Base/Timelines/Merge.swift
@@ -5,7 +5,12 @@
 
 import os.log
 
+public extension NSNotification.Name {
+    public static let mergedTimelineItems = Notification.Name("mergedTimelineItems")
+}
+
 typealias MergeScore = ConsumptionScore
+public typealias MergeResult = (kept: TimelineItem, killed: [TimelineItem])
 
 internal class Merge: CustomStringConvertible {
 
@@ -42,14 +47,25 @@ internal class Merge: CustomStringConvertible {
         if let betweener = betweener { store.release(betweener) }
     }
 
-    @discardableResult func doIt() -> (kept: TimelineItem, killed: [TimelineItem]) {
+    @discardableResult func doIt() -> MergeResult {
+        let description = String(describing: self)
+        os_log("Doing:\n%@", type: .debug, description)
+
         merge(deadman, into: keeper)
-        
+
+        let results: MergeResult
         if let betweener = betweener {
-            return (kept: keeper, killed: [deadman, betweener])
+            results = (kept: keeper, killed: [deadman, betweener])
         } else {
-            return (kept: keeper, killed: [deadman])
+            results = (kept: keeper, killed: [deadman])
         }
+
+        // notify listeners
+        let note = Notification(name: .mergedTimelineItems, object: self,
+                                userInfo: ["description": description, "results": results])
+        NotificationCenter.default.post(note)
+
+        return results
     }
 
     private func merge(_ deadman: TimelineItem, into keeper: TimelineItem) {
diff --git a/LocoKit/Base/Timelines/TimelineProcessor.swift b/LocoKit/Base/Timelines/TimelineProcessor.swift
index 194afc71..d34d9596 100644
--- a/LocoKit/Base/Timelines/TimelineProcessor.swift
+++ b/LocoKit/Base/Timelines/TimelineProcessor.swift
@@ -7,15 +7,10 @@
 
 import os.log
 
-public extension NSNotification.Name {
-    public static let mergedTimelineItems = Notification.Name("mergedTimelineItems")
-}
-
 public class TimelineProcessor {
 
     public static func process(from fromItem: TimelineItem) {
-        guard let store = fromItem.store else { return }
-        store.process {
+        fromItem.store?.process {
             var items: [TimelineItem] = [fromItem]
 
             // collect items before fromItem, up to two keepers
@@ -36,6 +31,21 @@ public class TimelineProcessor {
                 workingItem = next
             }
 
+            // recurse until no remaining possible merges
+            process(items) { results in
+                if let kept = results?.kept {
+                    process(from: kept)
+                }
+            }
+        }
+    }
+
+    public static func process(_ items: [TimelineItem], completion: ((MergeResult?) -> Void)? = nil) {
+        guard let store = items.first?.store else { return }
+        store.process {
+
+            /** collate all the potential merges **/
+
             var merges: [Merge] = []
             for workingItem in items {
                 workingItem.sanitiseEdges()
@@ -88,7 +98,8 @@ public class TimelineProcessor {
                 }
             }
 
-            // sort the merges by highest to lowest score
+            /** sort the merges by highest to lowest score **/
+
             merges = merges.sorted { $0.score.rawValue > $1.score.rawValue }
 
             if !merges.isEmpty {
@@ -97,21 +108,18 @@ public class TimelineProcessor {
                 os_log("Considering:\n%@", type: .debug, descriptions)
             }
 
-            // do the highest scoring valid merge
-            if let winningMerge = merges.first, winningMerge.score != .impossible {
-                let description = String(describing: winningMerge)
-                os_log("Doing:\n%@", type: .debug, description)
+            /** find the highest scoring valid merge **/
 
-                let results = winningMerge.doIt()
+            guard let winningMerge = merges.first, winningMerge.score != .impossible else {
+                completion?(nil)
+                return
+            }
 
-                onMain {
-                    let note = Notification(name: .mergedTimelineItems, object: self, userInfo: ["merge": description])
-                    NotificationCenter.default.post(note)
-                }
+            /** do it **/
 
-                // recurse until no valid merges left to do
-                self.process(from: results.kept)
-            }
+            let results = winningMerge.doIt()
+
+            completion?(results)
         }
     }
 
diff --git a/LocoKit/Base/Timelines/TimelineRecorder.swift b/LocoKit/Base/Timelines/TimelineRecorder.swift
index 716d0243..be77761d 100644
--- a/LocoKit/Base/Timelines/TimelineRecorder.swift
+++ b/LocoKit/Base/Timelines/TimelineRecorder.swift
@@ -33,11 +33,9 @@ public class TimelineRecorder {
 
     public init(store: TimelineStore, classifier: MLCompositeClassifier? = nil) {
         self.store = store
+        store.recorder = self
         self.classifier = classifier
 
-        // bootstrap the current item
-        self.currentItem = store.mostRecentItem
-
         let notes = NotificationCenter.default
         notes.addObserver(forName: .locomotionSampleUpdated, object: nil, queue: nil) { [weak self] _ in
             self?.recordSample()
@@ -51,6 +49,15 @@ public class TimelineRecorder {
         notes.addObserver(forName: .recordingStateChanged, object: nil, queue: nil) { [weak self] _ in
             self?.updateSleepModeAcceptability()
         }
+
+        // keep currentItem sane after merges
+        notes.addObserver(forName: .mergedTimelineItems, object: nil, queue: nil) { [weak self] note in
+            guard let results = note.userInfo?["results"] as? MergeResult else { return }
+            guard let current = self?.currentItem else { return }
+            if results.killed.contains(current) {
+                self?.currentItem = results.kept
+            }
+        }
     }
 
     // MARK: - Starting and stopping recording
@@ -97,7 +104,17 @@ public class TimelineRecorder {
 
     // MARK: - The recording cycle
 
-    private(set) public var currentItem: TimelineItem?
+    private var _currentItem: TimelineItem?
+    public private(set) var currentItem: TimelineItem? {
+        get {
+            if let item = _currentItem { return item }
+            _currentItem = store.mostRecentItem
+            return _currentItem
+        }
+        set(newValue) {
+            _currentItem = newValue
+        }
+    }
 
     public var currentVisit: Visit? { return currentItem as? Visit }
 
diff --git a/LocoKit/LocalStore/PersistentObject.swift b/LocoKit/LocalStore/PersistentObject.swift
index a6e28d7f..f5970196 100644
--- a/LocoKit/LocalStore/PersistentObject.swift
+++ b/LocoKit/LocalStore/PersistentObject.swift
@@ -17,7 +17,8 @@ public protocol PersistentObject: TimelineObject, Persistable {
     var transactionDate: Date? { get set }
     var lastSaved: Date? { get set }
     var unsaved: Bool { get }
-    var hasChanges: Bool { get }
+    var hasChanges: Bool { get set }
+    var needsSave: Bool { get }
 
     func save(immediate: Bool)
     func save(in db: Database) throws
@@ -26,8 +27,12 @@ public protocol PersistentObject: TimelineObject, Persistable {
 
 public extension PersistentObject {
     public var unsaved: Bool { return lastSaved == nil }
+    public var needsSave: Bool { return unsaved || hasChanges }
     public func save(immediate: Bool = false) { persistentStore.save(self, immediate: immediate) }
-    public func save(in db: Database) throws { if unsaved { try insert(db) } else if hasChanges { try update(db) } }
+    public func save(in db: Database) throws {
+        if unsaved { try insert(db) } else if hasChanges { try update(db) }
+        hasChanges = false
+    }
 }
 
 public extension PersistentObject where Self: TimelineItem {
diff --git a/LocoKit/LocalStore/PersistentPath.swift b/LocoKit/LocalStore/PersistentPath.swift
index a2039160..a2ea3599 100644
--- a/LocoKit/LocalStore/PersistentPath.swift
+++ b/LocoKit/LocalStore/PersistentPath.swift
@@ -16,7 +16,7 @@ open class PersistentPath: Path, PersistentObject {
         didSet {
             if oldValue != deleted {
                 hasChanges = true
-                save(immediate: true)
+                save()
             }
         }
     }
@@ -114,7 +114,7 @@ open class PersistentPath: Path, PersistentObject {
 
     public var transactionDate: Date?
     public var lastSaved: Date?
-    public private(set) var hasChanges: Bool = false
+    public var hasChanges: Bool = false
 
     // MARK: Initialisers
 
diff --git a/LocoKit/LocalStore/PersistentSample.swift b/LocoKit/LocalStore/PersistentSample.swift
index edbe8a5d..5c88a15a 100644
--- a/LocoKit/LocalStore/PersistentSample.swift
+++ b/LocoKit/LocalStore/PersistentSample.swift
@@ -93,7 +93,7 @@ open class PersistentSample: LocomotionSample, PersistentObject {
     public var persistentStore: PersistentTimelineStore { return store as! PersistentTimelineStore }
     public var transactionDate: Date?
     public var lastSaved: Date?
-    public private(set) var hasChanges: Bool = false
+    public var hasChanges: Bool = false
 
 }
 
diff --git a/LocoKit/LocalStore/PersistentTimelineStore.swift b/LocoKit/LocalStore/PersistentTimelineStore.swift
index 4ee4d3b6..8ee02353 100644
--- a/LocoKit/LocalStore/PersistentTimelineStore.swift
+++ b/LocoKit/LocalStore/PersistentTimelineStore.swift
@@ -212,10 +212,10 @@ open class PersistentTimelineStore: TimelineStore {
         mutex.sync {
             guard immediate || (itemsToSave.count + samplesToSave.count >= saveBatchSize) else { return }
 
-            savingItems = itemsToSave
+            savingItems = itemsToSave.filter { ($0 as? PersistentItem)?.needsSave == true }
             itemsToSave.removeAll(keepingCapacity: true)
 
-            savingSamples = samplesToSave
+            savingSamples = samplesToSave.filter { $0.needsSave }
             samplesToSave.removeAll(keepingCapacity: true)
         }
 
diff --git a/LocoKit/LocalStore/PersistentVisit.swift b/LocoKit/LocalStore/PersistentVisit.swift
index e7823140..4c83f4df 100644
--- a/LocoKit/LocalStore/PersistentVisit.swift
+++ b/LocoKit/LocalStore/PersistentVisit.swift
@@ -16,7 +16,7 @@ open class PersistentVisit: Visit, PersistentObject {
         didSet {
             if oldValue != deleted {
                 hasChanges = true
-                save(immediate: true)
+                save()
             }
         }
     }
@@ -114,7 +114,7 @@ open class PersistentVisit: Visit, PersistentObject {
 
     public var transactionDate: Date?
     public var lastSaved: Date?
-    public private(set) var hasChanges: Bool = false
+    public var hasChanges: Bool = false
 
     // MARK: Initialisers
 
diff --git a/LocoKit/LocalStore/TimelineSegment.swift b/LocoKit/LocalStore/TimelineSegment.swift
index a4454c32..0f7a758a 100644
--- a/LocoKit/LocalStore/TimelineSegment.swift
+++ b/LocoKit/LocalStore/TimelineSegment.swift
@@ -5,14 +5,21 @@
 //  Created by Matt Greenfield on 29/04/18.
 //
 
+import os.log
 import GRDB
 
 public class TimelineSegment {
 
     public let store: PersistentTimelineStore
-    public private(set) var timelineItems: [TimelineItem]?
     public var onUpdate: (() -> Void)?
 
+    private var _timelineItems: [TimelineItem]?
+    public var timelineItems: [TimelineItem] {
+        if let existing = _timelineItems { return existing }
+        _timelineItems = updatedItems
+        return _timelineItems!
+    }
+
     private let query: String
     private let arguments: StatementArguments?
     private let queue = DispatchQueue(label: "TimelineSegment")
@@ -37,14 +44,16 @@ public class TimelineSegment {
             self.observer = try FetchedRecordsController<RowCopy>(store.pool, sql: fullQuery, arguments: arguments,
                                                                   queue: queue)
 
-            observer.trackChanges { [weak self] observer in
+            self.observer.trackChanges { [weak self] observer in
                 self?.needsUpdate()
             }
+            self.observer.trackErrors { observer, error in
+                os_log("FetchedRecordsController error: %@", type: .error, error.localizedDescription)
+            }
 
             queue.async {
                 do {
                     try self.observer.performFetch()
-                    self.update()
                 } catch {
                     fatalError("OOPS: \(error)")
                 }
@@ -58,21 +67,17 @@ public class TimelineSegment {
     // MARK: - Result updating
 
     private func needsUpdate() {
+        _timelineItems = nil
         onMain {
             self.updateTimer?.invalidate()
             self.updateTimer = Timer.scheduledTimer(withTimeInterval: 0.01, repeats: false) { [weak self] _ in
-                self?.update()
+                self?.onUpdate?()
             }
         }
     }
 
-    private func update() {
-        var items: [TimelineItem] = []
-        for row in observer.fetchedRecords {
-            items.append(store.item(for: row.row))
-        }
-        self.timelineItems = items
-        onUpdate?()
+    private var updatedItems: [TimelineItem] {
+        return observer.fetchedRecords.map { store.item(for: $0.row) }
     }
 
 }