Man, I hate to read the rev counter (even though I really do). These are sports cars we're driving, and they should work fine, but on the other hand they have high output engines and their parts are more stressed than in normal cars.
I would assume that the belt and tensioners are designed to work at higher loads than what the engine gives, but the cut off is there to protect the engine from damage. I guess that means that you can't hit it everyday with no problem.
16 valve engines put higher stress on the tensioners, I've heard of 16v 33 having problems too with the canadian made parts.
The Q4 ripped the belt's teeth clean, it didn't snap. I saw the engine disassembled yesterday, the pistons luckily were OK, just a small insignificant mark on them. The valves, well eight died.
I hope this never happens to my engine. The parts alone would probably add to half of what I paid for the car.