I am somewhere in the middle on transmission bearings. You can test a bearing and since the ones in your transmission live in oil they usually hold up pretty good. all my two strokes pretty much get atf from the time they arrive with me and the only bearing that I seem to have a problem with are the countershaft bearings and then only when they get to me, or if a seal fails and it gets dirt in it. most of the ones that need replacement are probably from being subjected to a chain that was too tight. anyway, when i get in one for the first time that is the one I almost always replace, and much of the time it is just to make me feel better. So far I have yet to find a really bad bearing on the "dead" end of any shaft and that includes large 8-18 speed eaton/fuller transmissions.