They will last for generations. Someone mentioned that it was all in how it is riden. Owner/rider maintenance and care is the real secret. Usually, if you ride a machine like you love it, you will be acutely aware of what goes on, and react to any abnormal changes in sound or feel. Those who don't probably have the same problems with their 4-wheeled vehicles. I love every Harley that I own. I avoid city driving at all times, unless I absolutely must go there. The extra miles to bypass are just more scenery.
Jack
Jack