Average school boy stoner or graduated professional and functional addict? There is a bit of a difference. The majority of full time stoners, not exactly functional usually dealers could easily smoke 10-20 ciggarette sized joints in a day. A functioning addict could smoke 4-5 a night. Schoolboy stoners might smoke 2-3 a day.

4-5 a night is very common, at least where I've come from. I'd say about as common as someone who drinks 4 beers in a night after work. Not the total norm but not crazy or anything either.