Mace, My neighbor has the Power King's on a 38' King of the Road 5th wheel and has put several thousand miles on them with no problems at all. He still has the new unused spare mounted and the tires are about 3 years old now.
Once again i will say that driving habits play a big part in the longevity of any tire. I had a trailer years ago that ate tires left and right. Came to find out that one of the axles was just enough out of square with the frame and other axle and running down the road just dog legged enough to heat the tires up enough to blow due to the increased friction.
This is just my experience and my opinion, I hope you get it figured out. Good Luck!
