The overlay plating on the Clevite and the VP trimetallic bearings (VP bought a manufacturing license from Clevite for their VP2 bearings so both are Clevite 77) is microns thick. It's very soft to improve embedibility ie to absorb grit and stop it wearing the journals but once the overlay is full it has the opposite effect as the grit is hard. So fit an oil filter so the oil is clean and the grit build up in the overlay is minimised. Also as the overlay protects the next layer of leaded bronze from the acids in the oil attacking it as soon as any bronze shows from behind the overlay then the bearings need changing.