I'm not convinced I can keep my attention on one story for that long.

It's really, really hard. I think that's why so many people post WIPs--feedback can help you keep your focus. When I write long fic I don't post in progress (got burned doing that once), but I inevitably have to take periodic breaks during which I write something short and unrelated.

Long fics are my escapism :D

I think you're in luck. *g* There seems to be a pretty solid line up of people signed up.