I heard that turning off your phone once a day prevents “lag”. Other than stopping memory leaks (which could be more efficient by finding the offending app and fixing/deleting it) how would it help?
Probably not a lot else. Maybe trigger some cache-clearing or log rotation or something that could help a little.
I would say "can't hurt, but probably not very effective." It's probably just a holdover from when it was common advice because it immediately, noticeably helped.