That's what I was wondering. Are the plugs just going pop when you are trying to start the engine?? Are they giving up the ghost during the flight? Does the engine start and quit when you remove the glow driver? Are you using A clip on glow driver or A power pannel??
I have killed plugs using after run oil then starting the engine after it has sat A while but other then that my number one killer was putting the ends of my glow driver into the starter side of my power pannel. I have had plugs go out when I was getting that nasty gray metal stuff floating around in an engine that was wearing out.
Plugs burning out like that just isn't right, I can go forever on A OS #8.