I think I the quest for immortality and time travel goes hand in hand. Over the years ,people have been looking for ways to either keep themselves alive for a longer period of time or by making themselves look younger so as not to die early. These have caused genius mimds to wonder and work but has a solution been found till date? Nope.
Maybe simply coz there is a higher being somewhere who doesn't want us to live forever and his decision is final. Why do we keep trying all in the name of technology.
That's possible, but there's little doubt that the tools exist to extend our lives greatly. Personally, I would worry also whether the world has enough resources to sustain a larger population if this occurs on a broad scale.