This was the design flaw I mentioned earlier. I think the shaft itself will last indefinitely, but the way Dynamic put it together is what makes it a disposable bike. The whole unit is held together by only 3, small screws of about 3mm thread diameter, combined with only what I would estimate to be 2mm's of overlap on the bevel gears. Those three very important screws come loose regularly, when they do, the gears chip and gnash due to the lack of overlap in the bevel gears, eventually rendering them useless. The gears should have been spec'd with more overlap and there should be at least five larger allen screws or bolts clamping the the bottom bracket machinery together.