Originally Posted by Andrew R Stewart

For the numbers of external to shell bearings (Hollowtech) sold and their relative mid to better grades (as they are on more expensive bikes typically) I will say that we replace a lot. For the most part these are not really rebuildable and are regarded as disposable by the industry.

The tapered square BBs seem to be of better sealing in general and don't wear as rapidly. Especially since they are so much more common at the lower cost levels one might think their longevity should be less then external units. But our experience doesn't prove this assumption out.

I'm sure others will have their opinions, perhaps they can offer some ideas as to how many they see a year so we know the foundation their opinions are based on. Andy