I always have several in various stages of completion.
Usually I do finish a particular stage of the process on any one project before going on to the next project, unless I hit a snag and need to set it aside for a bit till I figure out how to make it do what I want it to or find the right fabric to move forward.
Do have trouble with getting the final stages done though. Once the top is finished I'm usually ready to move on rather than go through the hassle of sandwiching and quilting. Guess I need to make myself tackle some of those UFOs!