I believe this is a slightly controversial topic, at least from what I have gathered so far. Some say its best to leave the server on to spare the life time of the spinning rust. Other seem to prefer to save power and boot the server off each night. So wanted to chip in and hear what folks here do and why do what you do.
Bonus question; Do you guys have a UPS? Is it a must have for a homelab, or does it just depend on the usecase?
UPS depends on usecase and on the stability of your electrical supply (which varies greatly from place to place). I just leave everything running and have it configured to restart automatically on power restore (if it fails, which it rarely does).