Re- reading all of this again…..the simple answer is nobody knows . A lot of speculation, guesses, one metric comments, logical assumptions, anecdotal experiences, etc., but zero hard quants on multiple key metrics that support even a loose consistent lifespan model of any kind.
I find that surprising from the industry considering a high level of consistency in modern manufacturing processes, and materials, yet the absence of data may also reflect a common reality that data may show very little degradation, which of course is not good for promoting buy new. Who knows…. Again the only constant here from reading is we don’t know.