My experience with ceramic bearings on bicycles is the ceramic balls are incredibly high on hardness scale, but the races are typically too soft, relatively. The balls grind the races down pretty quickly, and if you add any water/moisture and the races are toast. This can happen in days or weeks. If you have a good waterproof grease, this helps ward off the moisture issue. Typically these bearings come with very light lithium, or similar, grease, which makes the problems worse.
Doubly important that they aren't sideloaded, as that would increase wear on the races immediately.
Maybe for a motor application where they're constantly oiled would work well enough.