Just a little FYI, having worked on a Funny Car team years ago, and also being able to hang out in the Force pits a bit I have seen a ton of spark plugs from both the older fuel engines and the new ones. The plugs don't always get completely eaten up on each pass, but the do get changed. I believe that the strain put on the plugs pretty much destroys the plug in the pass if the electrodes are not eaten completely up. Again, I've seen a lot of plugs and most of them are not completely destroyed during a run, but are really in bad shape, they are subjected to a lot from a fuel engine. And with the cost of a plug, it just hasn't made sense to risk re-using spark plugs when so much depends on the engine working at peak on each run.