i was actually wondering this as well. I just got back from Lake Tahoe and downhill its all downhill on Hwy50.
I dont like to ride my brakes, so i usually did a short pump to bring me from 65 to 55, then wouldnt have to use the brakes for another minute or so, so they would cool off. Thinking about it, this type of braking should be no more different than driving downtown. your brakes are spinning faster but you are using them at shorter periods and longer intervals between.
i was mostly engine braking though, i was in 4th and 5th most the time iirc. i dont like to engine brake too high though, i heard prolonged engine braking can lead to premature ring and cylinder wall tear. i think thats for mostly bikes and high compression motors but eh, i was hanging out mostly at 2k coasting downhill and only had to apply brakes in certain sections.
i would recommend against just keeping on them and riding them downhill. you will warp the rotors extremely fast.
1998 Eclipse GST Spyder - 14b turbo | 3" Catback | Evo8 BoV | 170fwhp if that
2003 Redfire Cobra - 448whp/435wtq - Sold