Ok that's not common by any means. Maybe a custom ROM or a new phone is in order?
Personally I reboot my iphone once a year. It also reboots overnight every 3 months or so for software updates, but that's often not observable because apps restore their state.
Not due to the above (the reboot need isn't frequent enough to bother me), but for other reasons, possibly? It's not high priority for me but I've been thinking about it. Thing is, I love my phone otherwise. An insane amount of resources go into making hardware like this, and the planet's already trashed enough as is; I hate throwing out hardware that works fine just for random software glitches I can easily put up with.
Personally I reboot my iphone once a year. It also reboots overnight every 3 months or so for software updates, but that's often not observable because apps restore their state.