How often you have to advance really depends on the thickness of the quilt sandwich.
I have a Hinterberg stretch frame and, when I first got it, I had to do as Gramie bj and adjust both sides. It wasn't all that time-consuming for me to do it, but definitely did interrupt the flow of quilting. I purchased Bower lifts and now it is much easier and faster to raise the takeup roller:
http://www.kathybowers.com/ . I think these are only for the hinterberg frames, though. The only roller I raise up is the takeup roller (underneath the arm of the machine). There is no need to adjust any of the other rollers.
What a lot of people do is install a dead bar. Basically this is an extra roller underneath the arm of the machine. You raise the takeup roller and install the dead bar below and maybe a little forward of the takeup roller. This means you never have to adjust the takeup roller. You keep it raised, and the dead bar keeps the quilt sandwich at a constant height. If you Google "dead bar on a quilting machine" and click on "images", you should be able to find some photos to help you see what a dead bar looks like.