I realize the answer to this question depends on a lot of factors, but is there a hard and fast rule for when to replace a chain? I have never replaced the chain on my bike in the last 8 years, but I do inspect it for strech via the 12" ruler per 12 links method regularly and its seemed ok. Anyway, I took my bike in for service and the tech said it MUST be replace every 3500 mile regardless. Seems a bit excessive.
What do people do?