I always have multiple projects going. Actually, I just saw a great suggestion on a frame quilting mailing list I'm on: one of the ladies doesn't finish her quilts as she goes. Since frame quilting is definitely a skill that needs to be continually practiced, she waits until she has 8-10 tops ready to be quilted and then does them all in a 2-3 week time span. She'll start with one of her charity quilts to 'warm up', then do the quilts from smallest to largest.