Queer as Folk was the first fandom I ever was really into, and I spent months watching and rewatching episodes. I was slow to the fandom, I actually resisted joining. I'd be sitting in our dorm room with raxhel reading her fanfic, and I'd think "Why is she reading that stuff?" I discovered vids first, and totally fell in love. I'd spend hours scouring the internet looking for vids, and even more time watching them. I eventually started reading fics (about 4-6 months in) and got wrapped up in LJ. In QaF though, the show was always what I was there for, first and foremost.
With Harry Potter, well I *really* resisted that fandom. I'd hear about how big and crazy, and mean, and did I mention crazy? that fandom was, and even though I loved the books, I just wasn't going to go there. I'd read the books though (often), and that was enough. Then I moved to China without a computer, and no internet, so I had to rely on fics that raxhel had saved on her computer. That's how I got into that fandom. HP was my shortest fandom ever. I lasted I think about 5 months before I was flammed and remembered why I had avoided that fandom in the first place. I had discovered Stargate by that point anyways.
Stargate I watched all at once (or, well it took us months since we were watching SG-1 and then SG-1 and SGA), and for the most part, I've only seen most of the episodes once. It makes it hard to vid in SGA because unlike QaF I haven't seen all the eps a million times, and couldn't tell you the exact second when character X said Y to character Z. The other thing that makes it really confusing is that I read a lot in this fandom. In fact in some ways I'm more into the fandom than I am into the show. Which means as I'm vidding I think I should *so* use that scene! And then realize that that was actually just in fanon and isn't actually canon.
Another result of this is, I sometimes forget what the characters really look like. Forexample, in fanfic people go on and on (and *on*) about how pudgy Rodney is. I know this was exaggerated in canon by having scene of Rodney being totally out of breath when running, or pulling out a powerbar, but there is so a difference between being fat and being out of shape. David Hewlett isn't fat. Like at all. Sure Joe is skinny, but that doesn't make Rodney fat in compairison, it makes him broad. I mean I was just rewatching rising and saw Rodney and Carson walking side by side and they had very similar body types.
Another person whom I'm always a bit surprised to see in the show is John. He's not as attractive as fic makes him out to be. I mean in fic he's always described as super handsom, or totally hot, or extremely attractive. And while I can't deny that John isn't hard on the eyes, I just don't find him that hot.