I have a solid that's been in my RR for 9 years. Usually it's break in, but now I wonder. I built 2 motors for friends. A BB Mopar and a SB Chev. Both ate cams about 7-8 years after they were built. Both sat for 6-8 months w/o being run every year. Maybe they were just run at Idle during Spring start-up? Don't know. I know the BB had Mobil one. I never got to tear them down since both went out of state. I think its a combination of poor lifter quality and oil type.
Doug