I've had very bad luck with tires on my dually due to separation issues. I'm only getting 15k to 20k before this happens and 3.5 to 4 years. I only have the camper on the truck about 3500 miles a year...
My last 3 sets of tires have been Sailun terramax AT's I moved from BGF all terrain ta's to them and couldn't be happier. I get about 10000more miles of tread life out of the sailunes, better traction in the winter, they handle the water on the roads better and run a little quieter on the highway. oh, and there less than half the price.