Just pointing out that life expectancy at age 40, which is when these astronauts flew, is 79.9 years.
No mod points today, so just reinforcing your statement.
The life expectancy figures cited by grandparent are based on a starting age of "zero". A lot of kids don't make it to age five, many due to car accidents. Once you've made it to age five, the "average life expectancy" of the remaining pool has gone up quite a bit.
As you move up the population pool age brackets, you have already lost the people who were going to bring down the average. To state otherwise brings you to the situation where you're introduced to an 85 year old man and say to him "you should have been dead five years ago!" In the case of astronauts, you're also dealing with a bunch of guys who are in relatively good shape - you've already weeded out the morbidly obese, drug addiction, etc.
The IRS actually has tons of tables in the XLS format for figuring this sort of thing out. They're used primarily in figuring out distribution of retirement benefits over time, but have other uses.