Originally Posted by stapfam
My group rides XC with plenty of hills. There is only one of us that changes seat height for climbs or downhills and he is always the last down and the last up. The rest of us have the competence to ride the trails with the bike set up for climbs, because that is where you gain ground.
In the situation you describe, as well as when racing, I agree - it's impractical to stop and constantly fiddle with seat height. However, the original question stated 1) you've been climbing for hours and 2) you have thousands of feet of descent ahead of you. In that case, it would be impractical *not* to optimize your setup by dropping your seat, which both lowers your center of gravity and transfers weight to the rear wheel.