alight, i have a quick, yet may come off as stupid to some, question. But is their any danger of running spark plugs to long? I know after awhile, and lots of use, the gap can widen and become larger, yada yada yada, but is their any danger in running one to long if you just re-gap it? the ngk spark plug in my lawn mower had been in there for 5 years, and i've never taken it out to check the gap. My question is, will running it to long without taking it out and checking the gap hurt anything, if it's still running good? it's running fine, so i don't see a need to pull it out, but will any "odd" thing happen, like say when a spark plug gets old, it loses it's "power" and doesn't fire good enough and stuff like, say carbon, can build up because the plug is old? If you do take one out and re-gap it, and put it back in, will anything bad become of the equipment because the plug is old? I know some people change their plugs every year or two years, but i can't see a reason for it, other than they just want a new one? If it's running good, why would they take it out and change it? to me it's just a waste of time, wear and tear on the spark plug threads, and waste of money, but is there a reason they do it?