there's a video on youtube or similar of the magura test bed.
Its an old pair of bomber forks with a hub being driven off a big electric motor.
They run them at various levels of force/speed and see how long it takes the brakes to boil. Seem to remember reading that the pads usualy became ineffective long before fresh fluid would boil.
Although it did make me wonder if they could develop a perfectly beded in pad, the market to DH racers must be quite big, especialy in the winter where pads last just a few runs.