Originally Posted by coachboyd

I would confidently say they are worry free as long as you use common sense. I can take my car down any mountain road around here, but if I ride the brakes in the car for miles on end I'll burn up the rotors. That being said, in all the carbon clinchers we have sold this year all throughout the world we have had one failure due to heat build up. It was from a 200+ pound rider who descended a 2.5 mile 10% average grade mountain. Normal times for this descent are around high 3 minutes to mid 4 minutes, it took him over 9 minutes to go down. He averaged 16.7mph (on a 10% downhill!). There was a prolonged period of time where he was going 12mph. Finally after 9 minutes of this the rear wheel finally started to bow outward a bit. He had thought it was just out of true when he sent it to us. The front wheel was perfectly fine which means he was really dragging that rear brake (which is even worse for heat build up).
So, we can't say they are "indestructible" (which we never tried to) and still encourage people to know proper braking technique. But I am confident the rims withstand just as good as any other carbon rim out there, even comparing to the companies who state they have never had a failure (despite there being two separate claims of them failing on Slowtwitch in the past week).