How would admin like to rotate out outdated private keys

[h2zh]

In the near future, when the entire key rotation task gets done, Pelican will support multiple active private keys and able to create a new private key every hour (or any arbitrary interval). Therefore, the directory containing the private key files will soon be flooded.

It is time to discuss how to rotate out (remove) outdated private keys. For example, How many private keys does the admin want to hold at the same time? How long would the admin want a private key last?