yeah maybe a account closure event so everything after key rotation event is invalid and everything before is indexed by relays on the new npub

You could still use the account on relays not synced with that. Besides relays are allowed to delete any events they want, so one could just delete the event and go on with the day. Another important nostr data note is that time isn't verified by anyone. I could post notes and back-/futuredate them however I want. There is no ledger.