Conventional wisdom holds that guitar strings should be changed every so often, and guitarists usually can tell the difference. What about piano strings? I surmise they don't suffer the same degree of wear as guitar strings--no frets, no plucking, no body oils/acids--but do they degrade over time? If so, does anyone ever change them for maintenance purposes, or is it way too big a job to bother with? (Just curious--I don't play piano.)