Ceramic bearings in motor vs steel bearings in high heat?

Does anyone know how 100% ceramic bearings handle heat compared to steel bearings?

I know the best thing to do with motor heating issues is to use bigger motors with more copper, but its only the last .5 of a mile that causes my motor temps to jump. Everything else in the motors rated to 300 F and the hottest I’ve gotten them in 4wd was 246 F and that’s at the very end of my route. 3/4ths of the way through and I’m only at 170 F.

The current bearings are rated to 210 F, which I’m passing, and thus they are starting to dry out (lose lubrication) and I can’t see them lasting forever.

Do cermaics have any properties that make them better for high heat?

These ones I found on ebay look promising. Any thoughts?

http://www.ebay.com/itm/4pcs-Full-Complement-Ceramic-ZrO2-Ball-Bearing-Bearings-6800-6801-6802-to-6816-/221793844873?var=&hash=item33a3f17e89:m:maobL3vmNhB_N3tY0_lfNGQ

Silicon Nitride (Si3N4) Ceramic Balls are formed from a new material suitable for applications where high loads, high speeds and extreme temeratures are factors. Long life and the need for minimal lubrication make this material appropriate for extreme applications. Silicon Nitirde is non-porous, non-magentic, non corrosive, lighter than steel and, in ball form, is harder than steel. Because ceramic balls are non-porous they are virtually frictionless and are capable of spinning faster than steel balls. http://www.bocabearings.com/bearing-types/radial-bearings/ceramic-hybrid-series http://www.bocabearings.com/bearing-types/radial-full-ceramic-bearings/silcon-nitride-si3n4-series