Jerry,
For clarification, do the SS bearings have SS races and steel *****, or SS races and SS *****?

Based on all the data provided so far it looks like the best solutions would be to switch to a roller bearing if possible or to go with the factory 6303 bearing and the factory size, or larger, idler pulley with a longer belt to fit. That would keep the Idler at the acceptable rpms and make it last longer. We still need to do regular checks on all bearings to catch them when they start to fail and not after they fail. Factory bearings are cheep enough, keeping a couple factory bearings on the shelf at home sounds like a prudent thing to do.

MikeR