Just wanted to put in another vote for McCoy #9 plugs. They have been ultra reliable for me. I change them out about every ten flights or so. Usually by flight #10 on a plug, the engine isn't runnig quite as well as when the plug was new, so it's time for a change.

BTW, for some reason, my plugs seem to go bad sooner on a pusher fan than a tractor fan.

b/r,
DFF