I had formerly thought that cartridge BBs just had to be better than the cup and spindle type, but after replacing a few (including one where the spindle broke), I am not so sure. On my all weather commuting bike, I have an 80's Sugino cup/spindle with loose bearings that must have close to 30,000 miles on it. When I cleaned and re-greased last year it showed little wear. I plan on continuing to use cartridge units, but with the expectation that they will need to be replaced every few years. Then again, perhaps I shouldn't buy the cheap ones that I usually do.