since there's so many attack bots out there constantly scanning you for hacks all the damn time your router is constantly dealing with connection attempts, even if its silent blocking them. This grows ARP tables, firewall logs, etc and sometimes this can lock up these lil ISP routers running off minimal hardware, especially when you get scanned very aggressively by a broken bot or targeted attack.. Ive seen big expensive routers crumble like this aswell, with minimal effort it is pretty easy to overwhelm a router's resources unless it was very well implemented.
There are things called hardware watchdog timers on alot of higher end equipment, this is an external chip that has to get a regular ping or it will reset the cpu.. the firmware will send a HELLO every second and if it ever stops for longer than a min it knows there is an issue and it auto-resets.. This is much more effective than a software reboot timer, and can be expanded to stop sending a ping if the network is unreachable, etc..
Software reboot timers are a bandaid if you have a slow memory leak that causes a hardlock; if you reset the device regularly it clears out the memory before it ever reaches an unrecoverable state.. If the software is sound and handles memory properly it will never be needed.. I would suggest disabling the software timers unless your actually encountering instability after a certain amount of uptime.
I am pretty sure the Ubiquiti PoE Switches have built in network watchdogs on them, my Ubiquiti EdgeRouter PoE certainly does.; some of the other higher end PoE switches will aswell... you basically configure the switch to ping the camera and if it cant for longer than is acceptable it kills the power for a few moments to force a reboot.