Heed to what your mechanic says not what we guessers come up with.
I keep two sets of plugs on hand, one in the engine and the other on a place board with six holes to hold the plugs in the cylinder position removed from.
I swap the sets every 7,500 miles to see the cylinder performance. I have nothing more important to do, so why not keep up on the engines condition.
You're going to be just fine.
Don't let anyone steal your JOY.
Happy Trails Beep Beep from Houston!!!
Donald, El Cheapo