And depending on the key disclosure laws in your country, you may not have a choice anyway.
An 18 hour reboot period is reasonable for people who use their phones once a day, and 12 hours is good for people using it all the time (accounting for sleep). Anything lower will just lead to inconvenience unless you ignore your calls/messages for hours anyway. If you don’t use your phone for days on end, 3 days is a good limit.