This is also helpful for those battery powered devices that you don't want powered all the time, as it degrades the battery.
Like, say, an old android phone spun up on your network as a Pi-Hole for ad-blocking.
Just have the power cycle slightly shorter than it usually takes to run out of battery power, and power it up for enough time to charge it.
Also, routers usually have an option to auto-reboot at specified intervals.
Finally, for Windows PCs, you can set up an automated reboot cycle with Task Scheduler.
For Linux PCs, you can set an automated reboot cycle by editing your Crontab.
For macOS, you can use pmset.