The Ford 6.8 V-10 lives just fine at the higher RPMs. The engine's computer will cut off the fuel if you try to rev it beyond its design redline. Just keep good oil in it, change it at the recommended intervals, and keep an eye on engine temps in extreme climates.
My last Class C had that engine and it never even hiccupped in the 9 years we had it. And we worked it hard! Mobil 1 full synthetic after break-in, Motorcraft filters, and I changed it about every 5,000 miles.
2014 Seneca 37TS
Toads: 2014 Ford Explorer Sport or 2013 Ford Focus ST