The real credit for that work is due to Mike Bodell, who wrote the piece and did all the research. I just served as editor/publisher. I learned a few things in the process. I now keep track of stylus usage with a simple click counter (of course, Mike turned me onto a very well made vintage unit). Clean records go a long way.
Incremental degradation is not apparent. I liken it to sneakers (or British "trainers"). You don’t realize they have lost their "bounce" until you put a fresh pair on. (Maybe it’s a dumb analogy). I think Mike mentions a reader who said his stylus was well past the normal conservative threshold and thought it still sounded fine, but then decided to send it out for a retip, and was pleasantly surprised by how much better it sounded after it was refreshed.
I keep an eye on the stylus just for basic cleanliness and straightness of the cantilever-using relatively low magnification. I’m not really qualified to examine stylus wear under a microscope, so have used various retipping services, including those of the manufacturer (who will often replace, or rebuilt entirely rather than just replace the diamond and clean up the cartridge innards).
I gather that the micro ridge type has a pretty hard limit at around 1,000 hours-- and that it should not be used after that. I had an Airtight Supreme done with that stylus shape, keeping the original cantilever. I had one Koetsu rebuilt by the factory before they went defunct. And have had a few others over the years- trade ups with Lyra, a rebuild by Van den Hul, etc.
I thought Mike did a great job in addressing the issue and called for more transparency within the industry about realistic wear/life, rather than quoting the absolute outer limit for a cartridge to function. Kudos to him!