I think the 12 years number come from the fact that a lot of cat’s die as kittens from accidents, illness,etc. Once they reach adulthood, I would expect them to live until they are at least 15. I’ve known several cats that surpassed the 20 year mark. but stay on top of vet care and if you haven’t already done so start putting money aside for future vet expenses as he gets older.
In my experience cats are living longer these days, just like humans are. They are generally getting better foods and better care. 12 used to be old age for a cat and most of the signs you see in a vet office still show that as elderly. Thirty years ago that’s about what my cats lived to be. However of the last group of 7 cats that aged in place with us two reached 16 and five reached 18 years. Our current family is all under five and we expect them all to live 18 to 20 years. All of our cats are and have been indoor/outdoor cats in rural areas. My friend’s cat is currently 22 and plugging along fine.