You're right -- their lube is crap too. I've seen some bearings that come packed with a lube I could not tell whether it was petroleum grease or chicken fat.

An idler won't have very high forces on it, relative to the size of the bearing. It just has to run continuously with a light load.

The Chinese bearings I've seen that disintegrate are in axles, disc gangs, etc, where the loads on the bearings are rather high. Lube helps, but won't stop soft steel from deforming and work-hardening in the bearing under a high load, which leads to metal failure in the bearing surfaces themselves.