If you have repeated failures using sealed ball bearings in a dirty environment here's the cure (not hypothesis -- this really works)
Smear a gob of grease onto both sides of the 2RS bearing then install. The gobs of grease act as a barrier and the effect is not subtle.
Rotobrator machine with steel shot for refinishing alternator cases and stripped starter housings.
Exposed bearings lasted 2 weeks in an LS brand rotobrator. Changed bearings gobbed on grease and they lasted 5+ years.
Delco CS-130 exposed rear 6000XX bearing. Common failures. Gobbed grease over exposed side, no more failures. Ever. This cure really works for all exposed bearings/