To clean bearing I invariably use petrol as I usually have some to hand. Any solvent that dissolves grease will do.
If in doubt as to the condition of the races have a look on the 'net for 'bearing failure modes'. There is plenty info from the likes of SKF including photos. Something to consider when viewing taper rollers is that they can have wear adjusted out - to a point.
With a typical bearing when play is detected it is binned. With a taper roller it is adjusted. Thus, it is possible to subject the bearing to wear that reduces the dimensions but without showing visible wear. The biggest danger is that a race wears so thin that the hard surface (of finite initial thickness induced through case or induction hardening) wears thin enough as to be unable to support the load place on it. What then happens is that it elastically deforms (returnable to original form) but the softer underlying metal deforms permanently and bit by bit the ability of the race to withstand load is reduced until it fails - catastrophically.
So, apart from the obvious scoring look for signs of this (any unevenness of the surface (IIRC it's termed false Brinnelling), anything other than smooth and shiny) and any sign of corrosion (pitting) also banishes the bearing to the bin. In the absence of any of that - reuse. (You are correct in preventing interim corrosion).
Looking at the two (race) photographs. In the first, presumably that is just dirt - not surface marking? In both, at the narrower diameter (of each) - a wear groove/ridges?
So far on this thread, two Scots, a man with Welsh roots, a smattering of English - when does the Irish Queen introduce herself?
