I purchase copper gaskets by the 100 pack and I change them out when I
rotate plugs on my airplane, but it is not often that I see a mechanic
actually install new gaskets when working on an engine... Just
something I tend to notice as I hang around airports...
Also, only a minority seem to use a torque wrench when seating the
plugs... Perhaps their hands are better calibrated than this lifetime,
shadetree mechanic... And not many seem to use plug lube...

There is maintenance that the owner can do on his airplane, and often
do closer to engineering specifications than the bored mechanic...
Now, before the licensed mechanics on this list jump on me, I am simply
reporting my observations from a lifetime of being an airport bum...
If you do a better job, then hooray for you...

Denny