What is best for your brakes when stopping at the bottom of the hill? You are at the top of a hill and want to stop at the bottom. What is best for your brakes so you don't wear them down:


brake continuously; or 
brake when you reach the bottom?
In terms of wearing out the brakes, they will wear less when you brake at the bottom.
When you descend a hill you have a fixed amount of energy to lose, and when you descend at a higher speed, a larger proportion of that energy is lost to wind resistance.

Practically however, brake pads/blocks tend to last a long time and are cheap to replace, wear is not really something to consider too much.  It's better to descend safely at a speed you feel comfortable with.