I logged 17, 399 km on FSA Carbon Pro cranks before the left crank failed - the carbon crank separated from the aluminum insert that slides onto the bb spindle. This was a 165mm track crank used exclusively on a fixed gear bike on the road, attached to an internal ISIS bottom bracket (probably one of the worst bottom bracket designs ever thought up! The first bb (Nashbar ISIS) lasted 14,260 km, and the one being used at the time (FSA-VP) was feeling quite loose and ready for replacement already).

I think that cranks used on road fixies are subjected to much higher loads than cranks used with multispeed bikes. I weigh 175 lbs, and on climbs I'm out of the saddle cranking on the 42x16 or 44x17. If I could drop down to 39x23, I'd be sitting down and spinning easily, with very little load on the cranks. So I would think that the wear on bike components installed on my fixie gets accelerated.

Also, the problem with ceramic bb's is that they need lots of attention. I replaced the FSA with a 165mm SRAM Omnium track crank with GXP bb. (BTW, I am not a big fan of SRAM's crank attachment method, but Shimano does not make an external-bb version of their track crank unfortunately.) I replaced the steel GXP bb with an F1 ceramic unit and didn't touch it for 13,092 km, at which point it was getting quite loose and needed to be sent back to F1 for maintenance. They suggested that for the conditions I was riding in (wet Pac NW), I should be popping the seals and adding grease every month or so. I've started doing this with the steel SRAM unit, and I think it's making the bearings last longer, so I've got the special ceramic bearing grease ready to go for when I reinstall the F1 unit for the summer.

Luis