re "dragging brakes" in general, cycco will back me up on this one -- its just not a good idea to drag brakes, any brake, for any period of time.
Good hard application of brakes to bleed off some speed, then let off to allow heat to go down a bit, then good hard braking again, repeat -- this is the same in cars as well, to avoid overheating and fading braking systems.
Dragging rim brakes or disc systems will cause overheating and fading, I've done this in cars as well as touring in mountains with bikes with rim or disc brakes.
I've toured a lot in mountains loaded up, and while I am a light rider, not dragging brakes is key.
It's all about managing heat and keeping it at a reasonable level.

I am however very comfortable at speed and judging safe speeds for the conditions.