The Making of Star Trek
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.
(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.
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.)
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.