I was a bit surprised to see this thread come back to life after 3 years! I'm still not finishing the quilts...
All the unfinished ones have now been bundled into the loft, out of sight. I decided that I wasn't going to drive myself to finish the ufos before starting a new project, but would work on whatever I wanted to do, old or new, on condition that it didn't join that bundle! So now I do try to keep my focus on just one, until it's completely done, with a back-up to pick up if I have to temporarily pause to buy supplies.
At the moment I'm making a quilt for a room that's been redecorated, and that's keeping me working on it, as it'll be the finishing touch and I want to see it in place. Maybe that's one of the keys - is there a good reason to finish a piece of work? I get my baby quilts done in time (with a lot of effort!). It's the ones that have no destination, that are being made for the interest, that tend to be put aside.