Actually, loopy, for 2007, I didn't book until October and I was still able to find a moderate-level room at Port Orleans Riverside. Lots of stuff
was booked, but it wasn't hard to find something. And there are approximately 1,000,000 other hotel options nearby that aren't Official Mouse.
I think post-holidays is a low-season time... so they can handle the influx of marathoners. We're a rowdy bunch, but not quite like folks in summer or right around Christmas

.
That said, I'm still going to book sooner than October this time.