[fasteddiecopeman]

I've removed/replaced plugs whenever I "do" my valves.

FWIW - they have NEVER looked worn-out, however my Mazda P5 has very similar-looking plugs, and my wife was complaining that the car would NOT maintain the speed in CRUISE CONTROL in a hilly area near Kelowna, so I replaced the plugs (which did NOT look worn-out) and NOW the car will easily climb that same hill in 'cruise'.

My TAKE - you can NOT tell anything on those plugs by looking! They're cheap enough to just REPLACE whenever you're 'in there'.

 

[fasteddiecopeman]

IF you get the SERVICE MANUAL, and the necessary TOOLS to 'do' the valves - you will spend LESS than getting it done by a dealer, and can do it MULTIPLE times, as necessary, and (probably) BETTER!

I believe that I have done it about 8 to 10 times on my '08, '09, and '15 V650s.