I recall someone mentioned a house rule that all teleports resolved at midnight
That's silly. And absurdly arbitrary. Do a lot of really wierd, arbitrary, corner-case limitations have to be put in place to achieve some small semblance of balance with a per-encounter system?
What about Dimension Door then, or other such spells? Dim Door is primarily a 'get outta monster's reach' spell, yet if you could do it at will, you'd have no trouble crossing the globe in a rather short time with it. If it gets changed to have a more limited distance, it will still be pretty effective. If it gets changed to a longer casting time or something, it loses its primary purpose.
Having only one copy of a spell active at any given time would really suck for some spells, too. 'Sorry, my wizard can't give the whole party Water Breathing so we can actually have an adventure in that shipwreck at the bottom of the lake, I can only maintain one at a time, and I'm not nearly high enough to cast a Mass Water Breathing, and it'd be pretty dangerous for just one of us to go down there alone.' Or 'Sorry, we can't all Fly across the gaping maw of the abyss, so I'll have to leave all you mundanes behind.' Or 'Well, I can't Mind Blank the entire party, so we better be on our toes 24/7, cuz that lich we couldn't stop last time is gonna Scry us and teleport in some kind of death squad at some point in the future, and probably come himself to Dominate one of you, since I can only keep myself protected against Scrying and Enchantments.' Etc.
I really, really just don't think going full-bore "per encounter" for balancing in D&D is a good idea. You'd have to totally rework the entire dang system and then everyone would have to wrap their brains around all the complicated new mechanics, whether they like them or not. And da%$it, I want wizards nuking stuff with Meteor Swarms! Not some nerfed, mangled mini-meteor cluster 'because it would be unfair to the warblade if wizards could do as much or more damage, and to a much larger area at once'. Per-day balancing works well for some stuff, dangit, and at least it makes some sense, unlike some of the other balancing methods.
Everything in moderation, y'know?