Their attacks get increasingly powerful as the seasons go on. It could be a progression -- why fight a daimohn with a 22LR pistol if you have recently come into a tommy gun?
One attack -- ideal for a fukufic -- is the manga-only Jupiter Coconut Cyclone. Da perfict ting take down da bid kahuna!
There have been fantasy novels by the bushelfull where a magician could only carry around a limited number of spells. Just assume Sailor Moon lives in that universe. As more powerful spells become available, the gentler ones are put away for storage.