Clifford Simak already answered this -- "Time is the simplest thing."
We are already dealing with it. The Human Being lives twice as long as other creatures of the same general size. Our lifespan has already been increased.
For me, it is a philosophy. If you are ninety years old, and you decide to plant a fruit tree, do so!
Plan for the future as though you will live forever, and enjoy each moment as though it could be your last.
You can't go wrong with that!
Time is the dimension of consciousness and there is only now. What's done is not anymore and what will be isn't either. Even if we could live forever, how could we possibly know that we are in the process of living forever? Living forever now? Seems like apples and oranges.