The Lifespan of an LP?

Never say never.

"You never hear me talking about flawed recordings. Instead what I talk about is how many I used to think were flawed, now come to life."

"That is why I have avoided buying Springsteen and the Stones, it is just too well known that their recording values suck."

"Which speaking of, a little birdie tells me there are some outstanding quality Rolling Stones albums, and Led Zeppelin. So I stand corrected on that. But not Bruce. Springsteen remains the King of Great Song, Bad Recording."

Better Records White Hot Stampers: Now the Story Can Be Told! | Audiogon Discussion Forum

"Year of the Cat on MoFi is so stepped on, so devoid of life and presence and detail I sent it off to Tom for entertainment value. Some clown on discogs thought it was worth $20! Pure crap, even compared to my random average beat up played a million times copy."

Early Stones recording quality on original Decca doesn't suck.  I wish I had bought them all, as the Stones had turned to c**p by 1975 (46 years of c**p from these geriatrics and counting).
My copy of 'Aftermath' still sounds great after 55 years and there is ~30 minutes of music crammed onto each side.  I must have played it quite a bit as well.

My original mono 'Blonde on Blonde' did wear out a long time ago but I was playing it on my father's primitive Collaro that set tracking weight with a spring and must have been running at 5 grammes or something.  You will know if they wear out; there was extraneous white noise.

What’s the opinion of “Last” record preservative?

Vinyl record is the best media format in the last 100 years.

Micro Groove records are the best, what is the reason to ask about lifespan if amazing records from the 50’s, 60’s, 70’s ... can be found in MINT condition or even sealed? Vintage records are the best sounding records, and believe me, they will last longer that all of us!

Used records from the 70’s are still amazing, they are 50 y.o. , so what ? 
Buy yourself a cartridge with advanced stylus profile and record wear will be minimum. 

No simple answer for this question. All depends on tt setup, pressure, adjustments factors  your way of spinning, storing and care of the records. Record’s production quality is factor too.