As you might know I'm a 27 year Toyota technician and almost all Toyota transmissions use Koyo bearings and I the only bearing failures I see are from fluid loss or contamination.
Toyota trucks use Koyo bearings on their carriers and go 300K without any troubles twocents
I use them in my rebuilds without hesitation up

Gus beer

64 Plymouth Savoy
493 Indy EZ's by Nick at Compu-Flow
5-Speed Richmond faceplate Liberty box
Dana 60