Have you looked at the PADI Tables? Up to about 100', you are close to an "A" diver after a 2 hr SI, which is very close to a clean slate.
Example:
Dive 1 @100 ft 20 min
2 hr SI
Dive 2 @ 100 17 min allowed
I used nitrox 32 on both liveaboards, and dove with an air computer, making it more conservative. Everywhere else I use regular air 80/20
Either way on a liveaboard you do a 2 hr SI, max 4 dives a day typically.
Maybe I've just been at it too long, but I like to do other things than just scuba on my vacations.