Personally, I prefer to just run the copper plugs (BKR6E) and change them out frequently. Especially on these higher mile cars that probably have some blow by. Long lasting plugs aren't that long lasting when the car makes them crusty.

There are exceptions to this. The S65 in my E90 M3, for example, does knock sensing through the spark plugs through some kind of bizarre sorcery. If you don't keep the plugs fresh (max 30k miles, preferably less), you'll lose a ton of power. And you can't swap to alternate plugs without dyno testing.

Oil on the electrodes means oil in the cylinder which can come from three problems.
1. Oil in the intake manifold from a malfunctioning CCV system
2. Valve stem seals leaking
3. Piston rings leaking

Start at the easiest to check and work your way down (#1, #3, then #2)
A. Look in the intake manifold for oil (fiber optic camera)
B. Compression test to check rings
C. If the two above don’t show problems, then it’s probably valve stem seals