[JoshuaDavid]

I don't know if it's particularly optimistic - if you're (accurately) saying current life expectancy numbers don't take catastrophic risks into account, neither did calculations of life expectancy back then. Unless you think there is a higher risk of catastrophic events now than there was during the cold war.

[fortran77]

Life expectancy has plateaued and may be trending down in the U.S. The culprit is likely obesity. (See https://time.com/5100737/obesity-lowering-life-expectancy-un... )