Charged items IMO were better when they had actual limited charges and just stopped working when they ran out. If you really wanted a way to recharge them, make it an expensive, lengthy, and/or hard to research ritual.
In fact, the ritual option would be a great way to deal with high level magic in general, which would also allow you to cap level advancement (insofar as personal power goes) at a lower, somewhat more manageable and relatable level. Continued advancement after that point could move into something like the domain game.
Guys! I've fixed D&D!
Gating the TRULY powerful spells as being rituals is something I'm definitely a fan of.
You can then make casting the spell a big adventure itself, the correct components, the correct situation, etc.