How many miles do you get out of your good tires?

I'd agree with 2oldman, about 4 years. Have no idea on mileage but they usually show age cracks before the tread is worn a lot. The more you use the rig the longer the tires should last. I've been told that tires have some sort of like lubrication or something that gets squished around when they are moving and when they just sit is doesn't move and keep them pliable.