In my experience it's been more pack a snack than a sleeping bag, the same for my family and friends, having said that most of the time they stay over and we smoke lots of changa
, obviously it's different for everyone but for us it's around 30-60 minutes after and if there are no other issues (being shook up from a difficult trip etc) then everyone has been ok and back to baseline able to drive.
Just pay close attention to yourself and if in doubt wait another 30 minutes or so.
LamVamRamYamHamKshamOm