Hi ScottM,
If your rig is 29 feet or longer with one or more slide outs, you might want to consider those extra-capacity E-rated tires. It's like 500 pounds more per tire which means 2000 more pounds for the rear axle and 1000 more pounds on the front. But there is such a thing as "too much". A shorter lighter rig with over-rated tires translates to a more harsh ride. Just about everyone would agree that the continuous earth-quaking when being driven is undesirable. You don't want to make it unnecessarily worse.
For our 24 foot (2007 E350-DRW chassis) rig with no slide out, I am buying new tires in the next few weeks. I decided on Michelin Agilis CrossClimate 115/112R. Discount tire gave me a price on 6 for $1316 out the door. Our rig is 14 years old with 38,000 miles and still has the original tires in-part because we garage our rig. I had such a good experience with the original Michelin LTX tires that made no sense to try a different brand. I also like that they are "Made In USA".