I like to have multiple projects going. That way if I am getting bored with one and need a break, there is something else I can do. I have 3 projects going on right now. A quilt top that is ready for me to get the backing pieced, then it's ready for basting and FMQing. I also have blocks cut out for another lap quilt. And I started working on a tote tonight.
I don't think I would have more than 3 or 4 projects going at the same time though. One thing I don't want are UFO's, and so far I have avoided that. So I like the variety, but it needs to be manageable. :-)