In my opinion, it is preferable if the pains of combat do not disappear as easily as it does in, say, Dragon Age. When you must resort to healing kits or Magic for healing, things may be more interesting. But only if said resources are limited. If you're swimming in gold to buy items, or if you can buy and carry items indefinitely, of if Magic is something easily acessible (if, say, the magic system is a mana bar that can be or is easily restored) then there's no point to not restoring hitpoints as soon as battle ends.