Gee, that's almost like asking a woman how much she weighs! LOL
I've only had one UFO and gave it away because I knew I'd never finish it.
I prefer to call my unfinished projects WIPs because I fully intend to finish them someday. I've got several in various stages of completion. I don't have a sewing room, so when I work, I tend to do more than one project so I can keep going. What I mean is that when I'm set up to piece, that's what I work on. Whatever needs piecing. When I rearrange the dining room so I can quilt, I try to do more than one while I've got it set up. It doesn't always happen though.