The problem of healing magic with infinite magic power

[Griffin]

So, here's one big problem I've been wrestling with:

Development blog: magic system and healing

Short version:

The magic system will be basically as it is in alpha 1: Spells cost magic power from your character's reserve. You can cast spells quickly, as long as you have enough power left. Your magic power recharges pretty quickly once you stop casting.

The problem comes if I give you a healing spell. If you have an infinite magic charge and a healing spell, then you effectively have full healing for free anytime you're in a safe spot. I have a couple of ideas for possible tradeoffs to make it interesting, but haven't really settled on anything yet.