5 years and around 10,000 miles has put metal fatigue in my bicycle. Bike shop found a crack in the frame when I brought it in for annual maintenance. They called to say I was eligible for the manufacturer's lifetime warranty on bike frames. That means a new bike for basically no cost. Moderate wear and tear can have some benefits.
Unlike the human body, bicycles can't restore themselves; with today's technology at least. A friend of mine marveled that things like human knees keep going as metal bike parts wear out. Nature does have some interesting ways. I think about my friend's comments when contemplating all the chains and freewheels I've gone through over the years. Moderate exercise is the trick