If you've never seen Through the Wormhole on the Science Channel, then you don't know what you're missing. It's not all geeked-out science, nor is it as grossly boring as a lecture in quantum physics. It really circles around life, and even the episodes that don't focus on life seem to circle around discovery and how it relates to life.
In other words, it's not all nerdy (though parts are: Dr. Michio Kaku is practically the Oriental Mr. Rogers who calls himself a conservative revolutionary... pffft) so fear not the incomprehensible depth or bore factor because neither is an issue.
There is a currently running episode or two focused on eternal life. They are truly interesting and in my usual form, I like to shop the minds of the greatest thinkers I can find to try to bring something to people that they can turn into a meal.
The theories gaining some speed seem to focus in a few different areas. In one, we manage to "upload" our brains and live that way, forever, by essentially having all of the information in our brain, including our conscious and such other intangibles, loaded into hardware. In another, we take it a step further, cloning ourselves and then downloading the mind, with all of its experiences, into the clone's brain, becoming ourselves again, only with a young body again and a new lease on life.
A couple of others are similar to each other; in one, the eventuality of the evolution of humans leads to our descendents being interested in our "time," and reviving it in order to learn about or experience it using their advanced technology, essentially creating a fake Earth with real people and events from the past (all of us) who, once created, never need to die again. The similar one suggests that time travel either is already occurring or will occur, and that anytime anybody "visits" a period that was during your life, you are, of course, re-animated and living again.
These are only a few that I've seen getting some respectable thought by thinkers among us; there are many others that are getting attention and more theories that are coming out every day. They all deserve a look, I believe, but I favor a few of these or some combination of them that makes a few things seem to be highly probable to me, and that's what I want to share.
First, although I'm not afraid to step outside of the laws of physics or thermodynamics or any other man-made "law" or "rule," when I propose a potential theory, I will stay within the confines of those laws for this post.
Time travel has not only been proven possible by mathematics already, but it has been proven physically (wiki is a good place to start if you wanna check those experiments out). While the science community wobbles on the legitimacy of the experiments and the research, most accept that if Einstein says something is definite, then it is at least possible and he was certain that space-time could be deformed, and if and where that happens (or when) time travel (and travel through space) will happen. I won't get into the time/space theories I like to probe that involve various events (I have many) like the Nazi Bell (a time machine, some suggest, designed by the Nazis) showing up in Pennsylvania in 1965 having jived perfectly with Einstein's theory--the thought that they indeed zapped from Germany in 1945 to land in PA in 1965. That's for another post... or book... but here, we'll look at how time travel and other theories suggested above will directly affect you, and how many days your brain will be allowed to exist, in total.
First, time travel. I say it's coming, or it's here. Do you? If so, this is the thing that beats me up about it: what are the chances that this moment is one you're living for the first time? If you are re-animated every time somebody visits the present, isn't it almost foolish to think that this just so happens to be our first time through? Mathematically, isn't it more likely that as you are reading this, this is your 50th, 100th, 10,000th time being in this moment? If all of space-time is connected, then this applies no matter which "species" of life is using the technology, no matter how far they are away. Arguably, they may not even have to land at a time that you existed--they may only need to pass through it in order for all of the moments between their departure and arrival point to be forced to exist again. That means you are popping back to life constantly as time travelers make their ways through time to see or experience or change whatever they are trying to do such things to.
Under that theory, you do live forever, but you never realize it.
A better theory might be this (I'll take one from above and just build on it a little): one physicist believed that eventually mankind would have evolved so far that every person and every moment will be brought back for observation... his theory was much deeper; I'm simplifying (his involved a tying in of meeting consciousness with God with all information). Here's how it can work. Look at the growth rate of our technology. It's fast. It's also accelerating. The only thing that's going to stop it is global catastrophes that take away billions of human lives and/or our ability to develop technology.
We have 4 or 5 billion years before the sun destroys our planet. We are already planning for colonizing the moon and I expect that the colonization of Mars is close behind. We will spread out. We will spread beyond our own solar system, and eventually, our galaxy. That's really a pretty safe bet. That whole, "Don't keep all of your eggs in one basket," thing has people realizing it's time to spread out just to keep our species alive. If you think about it, this isn't a lofty goal. It's a probability that borders on being a certainty.
So, we do.
Humans spread, and they develop, and evolutions begin "splitting." Humans living on a moon of Saturn are going to evolve differently than those on a super-Earth with different environments, populations, and events. What that means and what is really exciting about it is that if we humans now are essentially defining ourselves as a "missing link," that won't, of course, be missing--we are the core species from which many other families of humans will evolve. We are going to be, as they look back in 10,000, 50,000, and 100,000 years from now, the parent species.
Before I got off into another direction, though, as I'm prone to do, let's bring it back to how this will affect you and how long your mind gets to live, total.
You must know, just by the common expectation of eventuality, that one or more of those human-evolved branches of beings will come back. They will come back to this place and this time, and as their populations grow and grow, so too will their trips to "see" us. But what's different about this theory is that not only will we come back to life during each visit that happens in our time period, but they will have the technology to let us know it. That will happen either by simply informing us in ways we can't deny (showing us proof that this is not the first time we've been "alive at this moment") or they'll truly re-create us from DNA or some other science and anybody that can bring you to life using that kind of science will almost certainly have available to you the ability to visit any moments in your life however many times you want to with the clear knowledge that you are visiting a moment (or re-living it vs. just living it) in addition to that new life you'll be living that they have given you. If you want to tie this in with religion, go ahead; my problem is that religion is too simple, so I present a theory like this to say that even if there is no religion or none prove to be accurate or true, you are going to live again and you will have the option to live forever.
That, of course, brings up that question of why you might want to live forever. In my book, The Lost Dialogues of Table 18, there is some discussion of why we might even want to consider living forever... this life, filled with more pain than pleasure. All told, though, if you can live a moment or re-live it at will, couldn't you find pleasurable moments to live or re-live over and over, and won't technology have come far enough to give you a way to experience pleasure constantly, even as you explore new moments in your life (micro or bio-tech that essentially gives you the effects of a great drug, constantly)? Of course that will be available.
So, here's Kevin's good news for you. You're going to die, but you are going to be given life again--that I'm certain of, deep down. What I'm not certain of is whether or not you'll realize you're alive again. I believe it's coming--I believe that you will know you are alive again. I believe you'll have available to you choices on how to live those moments, through traveling to/through your past, traveling into the future, or just hanging out in the present, marveling at the choices available to you. In that, you can't find anything but beauty.