Clients should always update the relay hint (both on tags and on bech addresses) when creating events (don't just copy/paste what was there or what the user inserted). Good Nostr architectures log all relay hints seen for each event id, so that if it needs to load the id, the app has multiple options. When writing, apps should update the relay hint to the latest NIP-65 relay the author of that event is using IF that relay has the event.