Just finished a valve cover gasket R&R and replaced the plugs. The old plugs had 104k miles on them. I just bought the car at 102k. I'm surprised I've never had a misfire. See below for a side-by-side comparison of a new plug against an old plug. The old plug were the NGK's and the new plug is the Bosch.

 

you can google search spark plug wear and find that they can be fantastic indicators of engine problems. those plugs you have look like they have nice normal wear (the 4 electrode ones last forever) although they are alittle dark, meaning that you have been running a little rich.

 

The color and heat is mostly fine to me even tho I can see quite a bit of cylinder to cylinder variation. I can't do anything about the tune anyways.

I was only really concerned at how much the electrode was worn. It's worn down to almost be recessed into the insulator.

 

that is completely normal. i change my plugs once every 5k.. be glad you dont have the maintenence list of a B5 S4...lol...