I have never had a problem with a shutter that I know of, so not sure of how they might be tested. It just sounded like your count might be high with all the memory cards that you were going through. The folks that I have known with shutter problems on D300's knew for sure that they had shutter problems.
At 1st 87,000 sounded like a lot, but I can easily shoot 1,000 photos in a couple of hours. Shooting track meets, I usually shoot the highest frame rate, and keep my finger down sometimes for 15-20 seconds at a time. Don't even want to look at the shutter count on my D7000.