I changed the spark plugs on my 94 Q today (for no real reason, the car ran fine) at 96K miles and they look for all the world like the original plugs. The PO insisted the 60K service was done.

Go figure.

Most of the plugs were loose with some carbon half way up the threads. Much more so than I am used to seeing in an aluminum engine. Is this typical?

Being loose suggests they have been replaced. I have never seen loose factory plugs, but there always can be a first.

The carbon up the thread is because the plugs weren't tight enough.

i changed my plugs at 116,000 miles and they looked like they could have been original, except they weren't the same number as the book said. instead of PFR6G-11 they were PFR6B-11.