So I just looked at my Garmin Connect account for year to date mileage.... it's telling me well over 4000... I don't think either of my bikes that I ride the most would tell you they are worn out. It's the bike that site behind the garage in the rain for a month in the winter that you want to stay away from....... one that is ridden on a regular basis will tend to be in proper working order.
My 2 cents...