I don't know that I have that much light to shed, but I'm sure some have been running around for a very long time. It depends an awful lot on what part of the country you are in (salt), what motor and tranny are in the bus, and how they have been cared for. Physical things can generally last as long as someone is willing to take care of them, but taking care of them sometimes requires significant expense and labor. I think a lot of our rigs are pretty tired in the drivetrain as they approach 300k. People will say more, many will get less...but be prepared for any vehicle with more than a few thousand miles on the odometer and a decade on the calendar to need maintenance.