Right now all but one of them are all less than 5 years old. I bought the oldest one used. It's a 2001 and it currently has about 75k miles on it. All but one has the GM 5.7L / 6.0L gas drivetrain in them. One of them has the little 4cyl diesel in it. I haven't really decided at what point we will sell them. I kind of have a 10 year rule where I sell the trucks once they hit 10 years in age regardless of the mileage. My reasoning is that at at point they are still in good enough shape that I can get decent money for them. Aside from tires and general maintenance I haven't had any issues. I think we have done brakes on two of the trucks. I'm sure that the gas motors will never go as long as the diesel will but on the one with 75k miles I've never had any issues and it's the older 5.7L vortec motor.