It's the reason I won't run a truvativ/sram crank.
You have one size bearing in one cup, a different size bearing in the opposite cup, on a fixed application if you are a bit of an animal on the cranks the gxp setup will last 1/2 as long as a good quality square tapered setup. If you are lighter on the cranks it will last the same amount of time as a comparable setup, sugino 75/DA Track/Record Track.