At least in my case. I put platinums in about two years ago, BUT i probably used them for less then a year and the rest of the time my car was parked up. During that year or so it was parked my car would get the occasional one a week start up.
Anyway i replace the opti and bunch of other things. I find i have a high RPM miss. I take my platinums out look at them and they seem to be okay. I go ahead and replace them with TR6's and now my MISS IS GONE. I dont know if the platinums went bad from sitting or what, but even before the opti change i had the miss. Oh well just figured i would share.
Oh they were Bosch Platinums, just the regular ones.

 

Do you mean between the platinums? I didnt really check after i took them off. Now i did gap my tr6's at .035, and my plats were gapped stock. Maybe thats something i should take a look at, looking at them with right now they dont seem to diff but il have to gap check them later.

 

I dont know they all looked like normal plugs and the wear wasnt bad at all on them. Ive never experienced this with any other plug ive used. I had NGK's before these and they did great. I just chose the BOsh because i didnt wanna change plugs again for awhile. Guess that wasnt true.

 

Okay just checked the gap on my plats, they were all gapped at .050.