It's a crap shoot. A friend lost a lifters bearings in his '91 Evo on a local trip. When he got home, his oil looked like brown metal flake paint. On his roommates advice, he flushed the bottom end with ?? (solvent) while the cam cover was off. Put a new lifter in, and changed oil several times within a few hundred miles. He said the oil was less "sparkley" each time. He was still riding the bike 20 yrs. and 30k miles later. I know of others that have lost main or rod bearings with less metal in the oil/crankcase.