Settings & keep-time · Services and self-healing
How often does Storage Studio check whether a moved app was reinstalled?
Short answer: Every 10 minutes, and straight away when your external drive reconnects. If the app is open at the time, it waits until you quit it before moving the new copy.
The relocated apps watch checks every 10 minutes, and immediately whenever your external drive reconnects. If an updater has put a fresh copy back on your Mac and the app is closed, the watch moves it to the external drive and restores the shortcut; if the app is open, it waits until you quit it.
The last check time is shown on the Relocated apps watch row in Settings → Services.