Survive and reproduce...
So if/when one has the reproduction bit out that of the way, the survival bit as such may not seem to be quite as vital.
You know your genes are going to survive, meaning you don't personally have to. Which is the whole point of evolution, right?
I personally would prefer to survive longer. If you don't, that's your business.
Ideally I'd die in my sleep 75-80 +/- a few years having seen some grandkids. Doing daft stuff now to push that number further out just seems pointless.
The next generations will have enough problems to deal with without having one more cranky 90+ year-old constantly popping pills claiming he can live forever.
There's no evolutionary reason that survival instinct would turn off after a certain age.
Umm, without wishing to get too clinical or morbid, it's clear that once your offspring have reached adulthood there will always come a point beyond which you rely on them more than they rely on you, right?
Pretty much the entire point of civilization is not to be at the mercy of natural forces, including evolution.
The parent to my comment did bring up "survival instinct" (!)