I tend to believe that the experiences of most here are valid. What is true for one team at one time isn't necessarily true for all. We climbed & descended Mount Evans once about 8 years ago on the 4th of July. I remember the climb was long & difficult. Our old bike has rim brakes. We also occasionally installed a drum brake. I don't recall if we had it installed for that ride (likely so). I also don't remember how much we used it. The switchbacks near the top are tight & frequent. However it was cool (40s?) and I don't recall being concerned about rim heating. As stated earlier, the road surface near the top was pretty bad. Once we got below timberline, the curves opened up and we could carry more speed (didn't need to brake as much).
I have been concerned on some descents about brake heating but I don't recall this being one of them. Other descents at lower elevation with steeper grades and tighter switchbacks on hot days come to mind. I have tried to be mindful of heated rims under certain circumstances but we have never experienced any symptoms of impending failure.