Doesn't matter for the story series I'm writing. It picks up in third season and then goes AU from there. And I'm not particularly worried about staying in canon about magic, Slayer origins, and so on. I've got my own plot bunnies to send hopping around spreading terror.
I do understand now what I didn't understand when I started reading Buffy fanfic. That is, why the happy stuff is all set mid season 5. You've got to do a lot of repair work if you want to make those characters happy afterward.