I had this idea while playing, when a guy sprung a trap that poisoned him. He lost 1 point of Agility. I guess I wouldn't like a character to regain 1 ability point after 1 night of sleep. That's videogamey, as I can figure parties sleeping off days in dungeon to regain lost ability points. That's not like I would imagine the heroes of the late '70s!
I think I'll have character regain lost ability points during the time they spend between an adventure and the other to level up.
I think I might wanna do the same for spellburned abilities. It makes sense and enhances the drama of cutting your wrist to power up a spell!