I picked this post to illustrate a point. If you only use 20% of wear in 1200 hours then the "projected life" to zero tread left would be 6000 hours. I expect that it will be far less than that. I usually get 1000-1200 hours from my R1's/ Still plenty of tread left, but by then the sidewalls are "rotting" and the tires just give out. I expect that a lot of life expectancy is based on what you are doing with your tires. Lignt duty like mowing and pulling light rear implements will wire tires a lot less that heavy loader and other implement use that results in a lot of side wall flex.
Andy