Something I've always found problematic are spells with short term automatically recovered costs but long term benefits. Examples include Wall of Stone, Fabricate, Planar Binding, Animate Dead, Plague of Undead etc... the ones where you pay little or no long term costs (in the first three, often nothing, in the latter two, a small amount of gold) and in return get long term benefits (building a castle, creating stuff to sell, getting wishes or other services, getting minions). I feel like spells of this nature shouldn't exist at all... the cost must last as long as the benefit, if not longer. Most spells after all give a short term benefit (damaging the enemy, giving a boost) with a cost that lasts longer (loss of the spell slot for a day). Even though some of the long term benefit spells don't really break the game (Wall of Stone) I think it's a good principle to consider.
Some ideas would including making a spell like Fabricate cost more in long term costs (maybe it takes three times the normal amount of raw materials, so in the end the cost is much higher) and making some spells absorb the spell slot (As long as your animate dead minions are still up, you don't get the spell slot back).
Anyway, it's a thought.
JaronK
