As a parent who's been the primary caregiver for my young kids for years, it pains me to die when they aren't able to look after themselves yet. It is my one regret, really. So another 20 years would be cool from that perspective.
There's also the difficulty in forming any real plans, which often take a few years, if you don't have some belief that you'll live to see them through.
So telling ourselves "I'm going to live forever" (or at least 20 years more) is a basis for making long term plans like buying a house, having children, planting a garden...
I do not see much difference in dying in the next 12 month or next 40 years.