What do you think of this plug?

a lil story from my teen yrs...

I had a friend named roy, roy had a step side chevy w/350...
well one day he changed the plugs and it seemed to run a lot better.
2 weeks passes and he decides his milage has dropped and the motor doesn't respond as well as it did right after he changed the plugs, so he changes them again ...and again he feels that it runs better and picked up a mile or 2 per gallon of gas....

lame story short...
He went on changing plugs every 2 weeks from there on.

was it all in his head?
was it just that when you change plugs it runs better for a few?
was it that it ran better for a few....till the poor tune [rich from the quadropuke carb] slightly fouled the plug?

I say it will always seem to or run better initially after changing plugs, wether it tune or? but jmo

real question besides the pointed out quality of plug, as in different standards for the dealer vs the do it yourself'R parts store, IS....
Are the heat range specs the same for each brand per app? know what I mean guys?