Apparently, I'm not the only one who has trouble sitting for long periods of time. There was recently a discussion on the SAQA group that involved quite a bit of discussion about this common problem. For me, that's a dual problem. With my arthritis, it hurts to stay in any position for long.
With my Restless Leg Syndrome sometimes I can't sit at all. So, I've come up with a situation that works for me. I raised the table on some 2 X 4s. It's not too pretty and not quite finished off yet - it needs to be more secure so it doesn't fall off the 2 X 4s - but it works and does the job!
I can stand for hours and it makes my free motion stitching so much easier! My design wall is just behind me here so I can simply reach the next piece off the wall and sew!
I still have an older machine set up on the far side of this table if I want to sit and sew for awhile.