I agree they will never see racing RPMs. My car wont either. But what they will do is load their motorhome up with every thing they can pack and then maybe hook a small car/boat or what ever to the back and head out. When they get to the hills we have around the area I live in nor cal they will plant their foot on the floor and hold it there. The highways around here are 6% at least and some are 10%. The pull can last for an hour depending on your destination. This is where they build heat,heat and more heat.Its 100 plus in the summer and depending on the direction you are traveling ,there can be a prevailing tail wind stealing radiator efficiency.Brutal conditions and still some wont let up.The lucky ones boil over the radiator stop get towed what or ever. Some just burn flat to the earth right where they stop. I used to pass 1 or 2 per week in the summer when I was hauling lumber out of southern oregon into northern california. Certainly not all ford v-10s but you can see how even with very few miles these things take a real ass kicking.
Here is a picture of A motor on a test stand doing WOT testing.note the exaust manifolds. Ive actually seen this on an old gas powered dump truck behind the front tire going down the road in morning sunlight. brutal conditions.