Hey, I took my two month old hybrid into the LBS for a brakes and gears tune up the other day. When they called me with the quote they recommended that I replace the chain and rear cassette as I'd worn through the teeth on the cassette. I've been commuting for years (currently clocking 100 miles a week) but I've never struck this before. The mechanic in the shop advised me to replace the chain once a month(!) to counteract this happening. I'm all for maintenance but this seems to be taking it just one step too far. Admittedly, after the chain and cassette was replaced the bike rides like a dream. Has anyone else struck a rear cassette that seems to wear out too quickly and how often are chains being replaced?