Hopefully you use this braking technique to prevent brake fade:
DOT commercial Driver Manual:
5.4.6 – Proper Braking Technique
Remember. The use of brakes on a long and/or
steep downgrade is only a supplement to the
braking effect of the engine. Once the vehicle is in
the proper low gear, the following is the proper
braking technique:
• Apply the brakes just hard enough to feel a
definite slowdown.
• When your speed has been reduced to
approximately five mph below your "safe"
speed, release the brakes. (This application
should last for about three seconds.)
• When your speed has increased to your "safe"
speed, repeat steps 1 and 2.
For example, if your "safe" speed is 40 mph, you
would not apply the brakes until your speed
reaches 40 mph. You now apply the brakes hard
enough to gradually reduce your speed to 35 mph
and then release the brakes. Repeat this as often
as necessary until you have reached the end of the
downgrade.