what are you people doing that you are so worried about wearing through set of pads in a ONE hour race?
It is pretty rare, but over the past ~5 years I have ran into two races where disc brakes got thrashed.
The first one was a 24hours in the Old Pueblo race out in Tucson, AZ. It rained for pretty much all the night before and and most of the race leaving a course that had standing/running water on most of the trail and many swollen washes. With the desert hardpack trail there, a thin slurry of sand was constantly being sprayed on all bike surfaces. I went through 1.5 sets of avid mechanical disc pads, and 1 set of LX hydro pads over about 7-9 hours of racing. I actually ended up doing a few laps on a buddies CX bike, because after about 6 hours everyone on all types of bikes
had begun to wear through whatever brake pads they had and many of the extras brought. The locals and support crews hurried back to town and raided every bike shop they could, and still by noon the next day many people had just given up without hopes of replacing their brakes.
The second time was on a ~80km XC marathon race outside of Prague in the Czech Republic a couple years ago. Heavy rain during the race which had long hardpack gravel road sections resulted in more riding through flowing water. The base limestone silt of the gravel roads again coated everything, and I had to abandon 2/3 of the way in because I knew of two long technical downhills coming up, and I was already pressing pad backing into the rotors to scrub speed. I am aware of a few other DNFs, but most people on hydros and v-brakes seem to have not had as big a problem as I. To be fair, my pads were probably worn half way to start, but I just hadn't anticipated the poor conditions on what was supposed to be a reasonably short and easy race.
In both cases, I was actually breaking very little as they were both fast wide open courses. But the constant spray of fine grit on the rotors gradually wore away the braking material from the pads even when the pads were fully retracted. The second event even toasted a front rotor that I was braking on with the pad backing just in an effort to safely make it to a bail out point.
The 'perfect storm' conditions are pretty rare, by the are a real problem, especially for mechanical discs.
Now I haven't had the same conditions again yet, but I feel much more confident with my new XTR brakes, which retract quite far, and move to the rotor in 2 stages.
Hopefully Shimano's foray into CX/road hydraulic discs will incorporate some tech from these exceptional XTR stoppers!