Hmm, I am surprised I didn't mention this in the Atlases?! It is just now coming up in the next Shadowstone chapter
As I remember, full-blood elves require at least 2 hours of uninteruupted deep meditation (comparable to light sleep) per day to regain their PPs and feel rested, though they could probably remain awake and functional for days without any meditation if they don't need to regain PPs. Half-elves need real sleep (rem sleep) , at least 4-5 hours a day to be fully rested and alert and regain PPs.
Jad is kind of a special case, because as far as he knows, he is a Half-elf. Elves can actually sleep if they wish, though for them it is considered a waste of time. Jad has grown up sleeping at night, enjoys it and is used to it, and assumes he needs it.