Problem with Pump gas engines is most guys push the compression limits of this type of build and the engine ends up being on the edge of detonation. Now remember, Pump gas is VERY inconsistent and can vary drastically even from the same source.
Most times I recommend mixing pump and race gas on pump gas only builds if it's for racing or has more compression than it really should.
Any engine is likely to fail if not build right or taken care of...I've seen many high compression engines last years with regular maintanance.
Brian