A couple of issues here. Someone mentioned rotation and others age.
Most of what I know about tires and RVs comes from owning a 40' diesel pusher for several years, but not sure if what applies to a 31,000 pound vehicle is the same as what applies to a 11,000 pound vehicle.
That said, I was told more than once not to rotate the tires. The great weight difference between the rear and front made putting the rear tires upfront unacceptable.
Additionally, and this applies to all vehicles I think, tires should be replaced every 5 or 6 years (7 max if kept covered when stored) regardless of tread. The big DP tires never wore the tread down in 5 - 7 years, but from what I'm reading on the forum our OEM tire tread probably won't last that long anyway.
Buy the way, my DP came with Continental tires. At my first change I switched to Michelin. The ride was so improved I now buy only Michelin for all my vehicles and will do so when I have to replace the OEM on the Solera.