^^^^
What he said. I'm pulling a travel trailer on trips from 6,000 to 10,000 miles each year. I bought the truck with 231,000 miles on it and it's currently about to break 275,000. Proper maintenance on everything drivetrain related using the heavy duty use mileage specs in the manual (full transmission, transfer case, and differential services at 50k miles as opposed to 100k or 150k light duty use), Mobil 1 and a Wix or Purolator filter at 5k - or less if it's getting beaten up on the trip, etc. I did add a Diablo Sport AFM over-ride to keep all 8 cylinders operating full time which keeps the valve train fully lubricated during operation.
We're going to run the Oregon Trail and then head down to LA to see the Presidential libraries before heading back to Tennessee next spring. I'm fully confident it's going to do just fine.