I had a rotary Mazda RX2 the first year of production, I think about 173 or so. The thing ran very smooth for about 3,000 miles and then one had to change plugs. It simply consumed the electrodes for some reason. I found an add for triple electrode spark plugs in the JC Whitney catalog that look a lot like these and bought some. (a lot less than $9/ea) This set of plugs ran for the rest of the time I owned the car and performed like new. I took them out a couple of times just to check.
These are interesting, but it's so hard to change spark plugs in my cars now I probably won't try them.