What would make my old (yes, it's old) WB go through so many plugs? I've been through 4, this season. Seems they last less and less time, lately. And, I'm not using the mower any more than I have in the past. I put a new air filter on it just last week. I had to install a new plug, today. It didn't have 5 hours on it. I've changed the oil and filter, regularly. Admittedly, I use this machine in some REALLY rough stuff, occasionally. But, this is just a little absurd (IMO). Thanks.