Star in a Bottle

The area it covers is enormous, much wider than whatever room you hang it in, so one placed near the middle of a base reaches every crafting corner and bed you care about. A second only makes sense if your boss arena is somewhere completely separate. Wire it up if you want the light on a switch, but flipping it dark does not switch the effect off.

Raw regeneration on its own is small. The part mages notice is the shortened pause before mana starts coming back after a cast, which is what normally forces you into potions and then into mana sickness during a long fight. Hang one in the mechanical boss arena and count how many fewer potions you drink.