thats a balance queston not one about the system.
What im saying when i said spellslots make sense till AdND is that from Whitebox to ADnD the focus of DnD was un dungeon crawling. IE: adventures usually done in a single session (your character would die if you left the session in the dungeon, at least a lot of Dms did that) and in an enviroment where doing rests wasnt possible or hihgly dangerous, the time you spent in the dungeon was tracked and wandering monsters would discourage wasting time.
With the more narrative focus of DnD, vancian casting turned less into "this is what i have to work with for this adventure" and more "lets take a rest after 15 minutes cause i need to cast fireball again"
