diff --git a/README.md b/README.md
index 3d65d43e..424176b7 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,18 @@ https://github.com/pantheon-systems/wp-native-php-sessions
 
 That's it!
 
+## Configuration ##
+
+By default the session lifetime is set to 0, which is until the browser is closed.
+
+To override this use the `pantheon_session_expiration` filter before the WordPress Native PHP Sessions plugin is loaded. For example a small Must-use plugin (a.k.a. mu-plugin) could contain:
+
+    <?php
+    function my_session_expiration_override() {
+        return 60*60*4; // 4 hours
+    }
+    add_filter( 'pantheon_session_expiration', 'my_session_expiration_override' );
+
 ## Contributing ##
 
 See [CONTRIBUTING.md](https://github.com/pantheon-systems/wp-native-php-sessions/blob/main/CONTRIBUTING.md) for information on contributing.
diff --git a/readme.txt b/readme.txt
index 1508855a..bd9b4e37 100644
--- a/readme.txt
+++ b/readme.txt
@@ -29,6 +29,18 @@ https://github.com/pantheon-systems/wp-native-php-sessions
 
 That's it!
 
+== Configuration ==
+
+By default the session lifetime is set to 0, which is until the browser is closed.
+
+To override this use the `pantheon_session_expiration` filter before the WordPress Native PHP Sessions plugin is loaded. For example a small Must-use plugin (a.k.a. mu-plugin) could contain:
+
+    <?php
+    function my_session_expiration_override() {
+        return 60*60*4; // 4 hours
+    }
+    add_filter( 'pantheon_session_expiration', 'my_session_expiration_override' );
+
 == Contributing ==
 
 See [CONTRIBUTING.md](https://github.com/pantheon-systems/wp-native-php-sessions/blob/main/CONTRIBUTING.md) for information on contributing.