You only get a "Multiple Spark" at your plug if it's furnished by your Ignition Source. Even as far as the MSD (Multuple Spark Discharge) goes, I suppose it might help with Ignition, but I don't feel that you need it or that it works as well as advertised. Unless you have bad fuel or literally no gap at your plug, the first arc (what the spark actually is) from the electrode to the ground strap will light yer fire . . Anything after that is more or less, a waste of electricity.
A few years back, I tried a MSD on my Street Rod, a '34 Ford with a Blown SBC in it. I couldn't tell the difference from the old HEI I had on it. Nothing changed, started the same, got the same mileage, drove the same. Probably because if it was timed the same, and nothing was done to the fuel system, the MSD did exactly what the HEI had done before it. Set a fire with the first arc. (Spark)
But spark plugs, by themselves, don't do enough to change much. They're just a device to create an arc inside the Comustion Chamber when it's needed, everytime. High Cylinder pressure and lots of heat use 'em up but I dunno, I don't see a whole lotta difference between one and another in a well tuned Gas or Alky engine. If you have the right heat range, usually, in a race car, you'll just change them because it's a good idea, not because they're worn out.
The only time we change them is when the ground strap gets hard to read . . That's about twice in a season or when we change altitude drastically, and want to see how close to right we are on the tune up.
But, this coming year we changed to VP M 5 so there might be a little more heat than we've been used to. Have to pay attention.