Those things just keep on going. I also have one that was in working condition as of a couple of years ago, which was the last time I needed a spare. It probably still works. That PS/2 rubberdome survived a bath in hot chocolate and then being completely disassembled so that I could clean out the goop that had leaked in between the membranes, and went on to handle several more years of daily wear and tear before I splurged on a New Model M.