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...
No pics needed. As identified earlier, a big part of the issue is, you’re running those little tires to death IMO. Combined with either some bad luck, bad roads or cheap tires. You have a repeatable problem it seems so I’d expect to have to change something to achieve different results.