^^ This. Sometimes after a while they just get mushed down and bent out of shape a begin to weep oil. The ones I replaced and put in myself have yet to start leaking a few valve clearance inspections down the road. Maybe at the factory they are just a little more ham-fisted tightening down the cover bolts or what have you.
They're a consumable item, you can reuse it a few times, but eventually it leaks. Never hurts to have one on hand, you could try not replacing it and see if it leaks. If it does, slap the new one in. If it doesn't, save it for next time.