They wouldn't have to live that long, even under the currently understood laws of physics. Not from their perspective, at least. The rules of relativity say that as you approach the speed of light, time slows down for you. And as you very closely approach it, it slows way down.
can I ask kind of stupid question? Does the time slow down for the person going the speed of light, or does time slow down for those relative to this person? In other words, if you are in a mechanism that can travel the speed of light, you will still be in the mechanism for 4.36 years; but to those on earth, you got here just moments after you left.
If you slowed down time for yourself, you would have to become immobile, in a frozen state, its not like your body would get 4.36 years for free just because your body was traveling the speed of light (your heart should still beat the same amount of beats for those 4.36 years going the speed of light as it would have going 60 mpg.
But again, we're still at the same point: no UFO's unless the speed of light. And I don't think time slows down for he person going the speed of light, I think time slows down for those relative to the travel.