It has been 18 plus months or so since this thread was last updated. Poster "rauliruega" is spot on with his comments, observations and recommendations. However, he mentions that Ortofon published data on stylus tip wear. I have never been able to find such a document and I called Ortofon asking for it. So I think he means Shure and JICO, both did similar research on stylus wear hours. Their work pointed toward 400 to 500 hours of life for advanced tip shapes.
I recently took the same journey that Poster "rmm" took. What is codified in this thread is the reason why I was so confused also about critical stylus wear and hour of play life. All of the opinions expressed here are not otherwise supported by empirical research. They should be, while current cartridge manufacturers give conflicting answers to the question on critical stylus wear.
A record of my sojourn to learn how long stylus tips last is in print. As "rmm" did, I asked questions, and searched forums, looking for an answer. When I found, as in this thread, opinions that ranged all over the map, I did a deeper dive into the subject. This dive was driven to find out if my cartridge tip was worn to the point where it could damage my records. And I have a lot of records that I do not want to damage. I did not do any original research, while I am setting up to monitor my cartridge stylus tip with photomacrography. See this link to understand what that means: http://www.micrographia.com/projec/projapps/viny/viny0300.htm
I compiled everything I learned along the way into an written piece that was published in late May (2019) on The Vinyl Press. I found a lot of material on the subject that I believe will help answer your question.
See the link to my essay or discussion or article, whatever you want to call it, here: https://thevinylpress.com/the-finish-line-for-your-phonograph-stylus/
Also, see this thread for a number of terrific responses to this article: https://forums.stevehoffman.tv/threads/the-finish-line-for-your-phono-cartridge-stylus-wear-by-mike-...