I just happened to come across this article right before seeing your post-
http://www.healthonlinecentral.com/256-y...ets-world/
It doesn't exactly seem validated in a completely authentic way, but that's to be expected for any story that touches on an idea that breaks the status quo of what we believe is even possible.
Qigong and breathing exercises in general seem to point towards elongating life. I've heard numerous stories of yogis living to be exorbitantly old. You control your prana/chi and you control your vital life force. Knowing about really powerful Chinese and Indian herbs is helpful of course too.
As for infinite life, I haven't seen anywhere, whether in metaphysical/occult, religious, or Law of One teachings that point towards anyone having an infinite life in 3rd density, nor would one want to have a life that long for this particular life experience as far as I can tell. I feel as though the Law of One material points towards the answer in a more metaphysical sense. As we evolve spiritually, we experience much longer lifespans in higher densities. Then 7th-8th reaches the experience of eternity/infinity. Given where we are right now, I figure the basic Law of One response like that is already automatically granted. So, maybe there is more information out there that could point to more literal practices that can help you contemplate or experience what you're looking for.
One of my favorite films is The Fountain. In it, the main character searches for the answer to immortality, whether he's a Spanish explorer/conquistador searching for the Fountain of Youth/Tree of Life, or searching scientifically for a way to "conquer death", or traveling the cosmos a thousand years in the future trying to reach a place in the universe that is somewhat like the center of a galaxy (technically in the film he's traveling to a dying star Xibalba) so that he can attain immortality by possibly being the part of the birth of a new universe (or however you want to interpret his method of achieving immortality by reaching the star that will explode). The way I view it is similar to the Law of One perspective that I mentioned earlier, which is that it's not until he travels to a more metaphysical/higher density experience that he reaches what he's looking for.
That film is similar to the age old search by what could be considered the seeking by various adepts to discover the ultimate form of alchemy that can produce the philosopher's stone. As we are somewhat familiar with, the alchemical process within us is ignited as one seeks and heads down a spiritual path with increasing gravity in one's adeptness. The alchemical process becoming/being one that is more internal rather than external. Instead of seeking this elixir of life out there in the world, we can crystallize ourselves with greater and greater spiritual intensity that would make us come closer to being "immortal" as one comes closer to reaching "enlightenment". Some people believe in discovering a physical form of this philosopher's stone, however. And possibly that as we approach a more advanced society that can rediscover "ancient" technology that may have been seen in the time of Atlantis, there may be energetic technologies that far exceed our imaginations and extend life. Of course the more current technological method being looked at in this more mundane state of "advancement" we're in right now would be closer to becoming cybernetic beings where we can just swap/grow organs and host our brains carefully in this skull of ours that may be covered with newer and newer forms of whatever we surgically choose to look like. And then of course achieving some form of technological maturity that can simulate a convincing matrix. But that's the more mundane potentiality and not as interesting to me as the rediscovery of more metaphysical awareness.
In higher densities/ancient times there is some mention of a type of elixir of life or soma that would be powerful at creating either a powerful ecstatic experience that brings one closer to God or at least extends life. We may be able to see something like that in certain entheogens that bring one closer to an awareness of the nature of reality and takes one to a place or experience of eternity; when one comes back down, not much time has passed in this world.
Now of course the spiritual paths elucidated in the Law of One and other sources point towards the ultimate versions of attaining infinite life, as I mentioned earlier. In the Eastern/Vedic paradigm I've studied, there is an explanation of the spirit soul existing in a place that is essentially at a juncture between both the "material" world and the "spiritual" world (I am putting quotes around words that you can substitute with many other words depending on what terminology you feel more comfortable with). From this "middle" place, the soul can choose/look into either place. By one's desires/actions, one can experience what is in one's heart. Achieving the highest love of God is essentially considered the path that awakens one's eternal spiritual position. That person that has awakened that awareness is basically no longer attached to this material world and is existing in both places material and spiritual simultaneously and can choose to live fully in the spiritual world when desired. Generally those awakened beings will not leave because they want to help others find that love and awareness before leaving. But when that state is attained, there is an immense power that is gained, and if used in a particular way, could probably elongate life in this material body, but that is utterly not of interest because eternal, blissful life has already been awakened and is being experienced.