Yeah, the Relay should at least try to monitor its own state and try to do a self-reset when needed. (Even if only via a WDT.)
It should also try to let the owner perform a remote reset. An external device is always an option, but it shouldn't be a required option!
As a last resort, the Relay should support scheduling a periodic reset, perhaps every night.
The Relay is fortunate, being wall-powered. Battery-powered devices are a more difficult problem (but are hopefully also simpler and less likely to lock up).