I only change gearing incidentally when changing bikes. If I know I'm not going to climb too much I might grab the bike with a 34x28 instead of the bike with a 34x32. My lightest bike has a 34x30 so if I'm feeling like giving that a go I might take that one instead of the 34x32, but it's because I'm looking for a particular riding experience, not because I'm more fit and don't need the 32.