It's amazing how small the difference can be. I ride with a Selle Anatomica seat, and over the course of a few weeks it stretches enough (still under 2000 miles or something) that I drop something like 1/3 of an inch. Before it gets uncomfortable, I start to have my quads start just KILLING me on the two hills on my daily commute. Quick twist of the screw and it's wonderful again, but it's surprising what a difference a miniscule adjustment can make.