The alarm on my Google pixel goes off until I turn it off. I've come out of a shower to find it still going off 20 minutes later if I hit snooze instead of stop. I am sighted though, so I can't speak to how easy it is to set the alarm for someone with low or no vision. It is pretty set and forget though, and resets for the next day when I hit stop.

I wouldn't say it's excessive. If you're not using that phone for anything, might as well give it a good second life. Also, that is surely lest excessive than getting a Raspberry Pi involved, no?