Every once in a while, someone complains that clerics are way overpowered compared to other classes because they can "absorb more damage" by stocking up on healing spells. I don't really agree with that, but I'm not going to address the argument itself. Instead, I'm going to suggest a fix: characters can only be magically healed once per adventure.
There's some precedent for this. The clerical turn undead ability works only once per creature per encounter, at least in some early versions of D&D. It does have the benefit of not requiring any change to the cleric class itself, just to the way Cure Light Wounds and Cure Serious Wounds are interpreted.
This, of course, reinforces the idea of short expeditions with frequent trips back to town. Some people complain about this, too, although I see it as a desirable feature.