I agree its not just on Jayco's. I've seen it on more than a few other trailers with the dark cap. My Eagle HT still looks nice on the cap, but im sure I'll be dealing with fading before the warranty is up. I plan to put mine back in a lighter color like the sides.
2013 Ram 3500 Laramie Cummins
2014 Eagle HT 29.5 BHDS