The Lifespan of an LP?

There is a huge factor over which we have no control -- the vinyl compound itself. Most of the plastic today used in records for the US comes from Thailand, I believe, and like a custom butcher that sells to restaurants, can make a proprietary compound that is a "secret." You won’t to my knowledge get the exact details and what could you do with the information anyway? In terms or residual noise, consistency of materials, there are a lot of other variables too.
That old MoFi JVC Supervinyl was the bomb. I played some of those records to death, and while in many cases not my preferred pressing now, those copies, which I had from the ’80s, are still quiet, tick or noise free and no apparent degradation over a more than "good" system.
Luck of the draw in some cases-- certainly today when you see what comes out of places that I’ll refrain from naming. (Rainbo-- stuff was horrible, even though they could make a good record; now out of business).
People swung to Japanese vinyl during the oil crisis and through the death of vinyl in part because of the quality coming from there- safety copy or different EQ be damned (On some music it's very neutral but that’s a subjective factor too).
Old vinyl- all over the place. I’m more interested in what it was played on than how many times it was played. But, don’t know that either in most cases in the used market. I have old records that play great and have seen some play here over the years- copies I know I’ve had for a long time. In some cases, the stylus may be in contact with a different part of the groove, and that may make a difference too, as would how your entire phono section works together. See @Atmasphere re noise and phono stages, loading, etc.
And some vinyl is just inherently noisy from the get go- and also very immediate in its sound, like you get one with the other, but that’s not a consistent truth either. It’s pretty much case by case, and every copy of every record has a history.
I had new copies of one record that played clean the first time, but afterwards had ticks and pops. Record had been effectively cleaned to beyond archival standards. I think it was just a soft compound, but I don’t remember cueing individual tracks, which I certainly did back in the day on records I’ve had for years, and they still sound great-- fresh cartridge, high end table, etc.
Short answer: depends.

@wolfie- The "Shure" study that you are referring to is likely Harold Weiler’s "The Wear and Care of Records and Styli" published as a book(let) by Climax in 1954. Mike Bodell used it as a starting point for a more recent article on Stylus Wear-- questioning the long lives claimed by some cartridge manufacturers for stylus life. Although some readers were skeptical that Weiler’s findings- using a conical stylus and heavy tracking force--were still relevant, Mike did a good job in pointing out the comprehensive approach Weiler took, including evaluating stylus wear at certain early intervals that were noticeable to people who QC’d records at pressing plants. (Yes, they really did do that once upon a time). One of the folks who helped Mike with the macrophotography did his own running experiment on stylus wear and was able to look at the results at different intervals up to around a thousand hours, when he stopped. (It wasn’t a formal study, but the person did put some controls in place and shared his findings-- very little wear, surprisingly, at much lower tracking forces, lower than those I use currently with modern high end cartridges).
One of Weiler’s postulates-- I’m not sure if it was proven in the paper, I’d have to go back and re-read it-- was that diamond dust from the stylus left an abrasive residue on the record that exacerbated wear of both the record and stylus. As far as I know, there is no scientifically vetted study establishing this, but it raises an interesting point about record cleanliness and stylus wear.
And at a certain point, the worn stylus may damage the grooves. Too many variables to say when with any precision. Chances are once you begin to hear audible degradation, you are at that point-- whether to continue playing records without damage is a question.
The problem is also one of incremental degradation-- you think the thing still sounds fine after 6 years of constant use, but one person who questioned the applicability of Weiler’s work to the modern era with advanced stylus shapes, good tone arms and care decided to send his Decca back to the UK to be gone over despite the fact that he heard no degradation. Turned out the stylus was quite worn, the cartridge rebuilt by the factory and sounded considerably better on its return.
All of this is obviously interrelated to the question of record wear, including proper set up of the cartridge in the first instance.