Errr, I did some 120000 words before I decided I had made a couple of creative mistakes at some points that needed complicated rectifying. As it is only a fan piece and won;t ever get me anywhere it wasn't worth making a huge effort to do all that and I moved onto other things. Still, always nice to have something to come back to later.
Well, my main project has always been a fantasy job that I have started at least 15 times, once got as far as about 150000 words. It was a gift for my girlfriend. I MUST get back to it again, actually, and get a start I am happy with.
Other than the HP stuff through I am not a huge fan fiction writer.