They seem to have significantly more than two hours of homework a night. It seems like they get roughly two to six hours of homework per week for each of their classes (some of those teachers *cough*McGonagall-and-Snape*cough* assign rather extensive essays), so when they have Potions, Defence Against the Dark Arts, Transfiguration, Charms, Diviniation, Arithmancy, Ancient Runes, Care of Magical Creatures, History of Magic, Muggle Studies, Herbology and Astronomy, even if they're only taking half of those classes, twelve to thirty six hours of homework a week is a bit much, especially considering that one day a week is completely screwed up by having Astronomy at midnight, and class from roughly nine to five, and whatever other extra-curricular activities on top of that (Charms Club, Dueling Club, Gobstones, Quidditch, etc)
Originally Posted by squirrly donut
Trelawney's dream diary, if properly done, would probably have taken between two and eight hours per week to do properly.
So I'd go with six to eight class periods, if you assume one of those was a double. So, really, seven periods, with one of them lasting longer than the other. Every day, because they seem to get Double Potions twice a week.