Well Dick, you've lasted so long because that ball and cage valve is so robust. The technician who put it together did a great job
As an aside, does your valve make noise?
My Starr-Edwards "ball-in-cage" valve was designed and built by a young heart surgeon Albert Starr and a young electrical engineer Lowell Edwards and the design relied heavily on an 1858 patent for a "bottle stopper".
I think it did make a clicking sound in the beginning.........but I haven't heard it in years.