I have P275 / 65R18 Goodyear tires. Treadware 500, Traction A, and Temp B.....and they only have 35,000 miles on them. We took a long 2,500 mile trip last year and it took a huge toll on tread ware...
There are tires that last but I don't think you'll like them for winters in Colorado. Lose the P tires and switch to LTs should see a gain. I would expect good wear out of Nitto Dura Grappers in 275/65/18s.