I used to alternate between sitting and standing. I don't need to any more. The trick for me, figured out by a therapist, was to build the proper muscles, and to always hold proper posture. I find that I can sit anywhere with comfort now, even on the crappiest chairs, because I use my muscles to support me, not the chair. When you stand, you do the same. I've come to appreciate the importance of our muscles and how they contribute to one's quality of life.