I think if you have problems to start with you'll have problems with aches and pains...whether you're quilting or doing any other activity for a long time.
I have a longarm that I stand at for hours...usually without problems....as long as I'm standing correctly, of course! I take breaks and MOVE to get the blood flowing. Perhaps changing a load of clothes (bending and stooping), going up and down the stairs, laying down on the floor to stretch or riding a exercise bike for a few minutes.
...and then there could be an entire discussion of what shoes to wear when standing for long periods of time!
I stand at my cutting table which is at least 36" tall and sit for all sewing machine sewing....even binding a quilt.
Nan - Indiana