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

I've owned a pop-up and had to cha ge 1 tire in 6 years. Never changed the factory tires on my Dutchmen. Changed factory tires on my Springdale in its 5th year,sold in the 7th year. Still on factory tires on my Outback (11 months old). My Springdale tires dry rotted, other than that they were still good. Mine are not about mileage, mine are about "years".