approaching 50,000mi on original lifters [98 dyna] run se-4 cam and se heads which have a stiffer spring pack. after hearing stories of scrambled oil pumps and lifter blocks because of lifter failure i am debating whether to change them out as preventive maintenance. are there any signs of them going bad so you can catch it in time or does a roller let loose and that's all she wrote? any/all replies appreciated.