Axle bearings: how to tell if replacement needed

I just checked them and they seem nice and smooth. Probably need a good cleaning and new grease tho. Can this be done with them still on the axles.
Sorry abouth the confusion earlier. Once I put pressure against the bearing ( pushed the outer sleeve/ring towards the axle flange) the jiggle went away.

If I can clean them and grease them, while still on axles, what's the best way.
Thanks again guys!!