On a related note, what is the assumption of Vulcan life spans in the novels? The shows portray that even though Sarek died from a degenerative mental disease and looked fine physically at 202, T'Pol in E^2 looked decrepit at about 185. I tend to assume that Vulcans' lifespans average about 300. It's something that annoyed me, that the T'Pau from "First Steps" somehow couldn't be the T'Pau from "Amok Time" because it was 200 years later! (Obviously ENT gave a better reason.) If Vulcans only live to about 200 and humans to about 150, it really makes Vulcans' attitudes about living so much longer suspect.
The Making of Star Trek (published in 1968) established that a typical Vulcan lifespan was about 250 years. So I've always taken that for granted. But as you say, it seems the later shows haven't always followed that lead. Still, Sarek died of a degenerative disease, and alt-T'Pol had been suffering the ravages of the Delphic Expanse for over a century. So they may not be typical cases. I don't know what you mean. Clearly at the time "First Steps" was written, it was intended to be the same T'Pau, but then ENT established that T'Pau was born in 2122, rendering that impossible. So the fans came up with the retcon that the T'Pau from "First Steps" was a different person of the same name.
Didn't one of Jean Lorrah's novels ("Vulcan Academy Murders" or "IDIC Epidemic") have a 300+ year old Vulcan? T'Pau was also in a New Frontier novel. She must be approaching that age herself.
I don't remember, but if the average is c. 250, then it stands to reason that the maximum could be as high as 300, which is only 20% greater. It would be the equivalent of a human living to 105 or more, which does occasionally happen. As stated above, her canonical birthdate was 2122. Thus, in 2382, she would be 260, just slightly above the average asserted in TMoST.
Unless they all got zapped by some kind of slow-aging-ray or injected with Nick Fury's Infinity Formula on some mission that we never saw!
McCoy and Scotty were both exposed to alien medical care beyond UFP understanding ("For the World is Hollow" and "The Changeling", respectively); Spock was brought back from the dead by the Genesis effect; and Kirk was put through the grinder multiple times, including a body-mind swap in "Turnabout Intruder". In addition, Kirk, McCoy and Spock all received kironide injections that gave them the same supernatural powers enjoyed by a group of very long-lived humanoids. So basically all the TOS heroes we directly observe enjoying long lives could be doing so because of alien meddling. Or then all of them could be suffering from premature aging by the standards of the day, due to all the life-shortening experiences listed above and elsewhere. They did all suffer through "The Deadly Years", after all... Timo Saloniemi
My view is that humans NATURALLY live to be about 80s or their 100s but that extraordinary medicine can be used to keep them fit or firm into their 200s if they choose (where they'll be completely decrypt). I wouldn't be surprised if there's "regeneration therapies" and organ replacements at a fairly regular rate. I also tend to view a certain quality of life element that a Starfleet Captain with access to Federation tech nonstop is going to be better off than your average citizen on a colony world. So most people would live until they're 140s or 150 then just let themselves die than trying to squeeze EVERY moment out of their lives.
But they were "reset" back to their proper ages via an injection. I've always thought it possible that they weren't truly cured, that they still had the aging disease, its just that it was reset to age them relatively instep with their natural clocks. But at anytime, if injected again, they would again be reset to their initial biological state, and this time the disease would be aging them really slowly.