I tow a 6,500 lb trailer many times a summer, including up and over the Appalachian Mountains. I made a few simple but very effective changes to the stock brake system to handle the heat and resist fade:
Centric StopTech (formerly StopTech Powerslot) slotted front rotors, not much more expensive than quality stock rotors
Centric Fleet Performance brake pads- higher coefficient of friction, better fade resistance
ATE SL brake fluid- high quality DOT4 brake fluid that's original equipment in AMG Mercedes cars. Dry boiling point of 536 degrees where regular DOT 4 is 446.
I have never experienced fade. Even had the Denali on the race track once just for fun, repeated stops from over 90 and the brakes were fine for several laps before they started to go away, but that's probably the worst extreme possible.