I am refurbishing a bike and am deciding how much to clean out the rear derailleur. It's in pretty good shape. But after I take off the chain, I tried spinning the jockey wheels with my fingers (after cleaning grime off the sides), and they only spin as long as I'm touching/pushing them -- they don't spin freely. Should I be concerned enough to take apart the derailleur and clean/re-oil or re-grease the jockey wheels?
If the teeth on the jockey wheels appear to be in good shape then you probably have nothing to worry about. Many jockey wheels use bushings instead of bearings, and either way they are not going to spin for very long just because there's not much weight to them and therefore they don't carry much inertia.