I was listening to the radio the other day, for those of you in Australia it was Doctor Karl on JJJ, a walking encyclopedia, he was saying that nobody realy knows why we die of old age, but that our cells are programed to grow old, and theoreticaly if we could reprogram ourselves in such a way, there is no reason why we couldn't maintain the body of a twenty year old for as long as we could support it, so at least as long as we can exist on this planet.
It's of course been noted that Yogis can do extrodinary things to their bodies, one guy has been recorded to create a 16 degree teperature difference between two places on the palm of his hand, and I'm sure there have been cases of much more extrodinary things that this, though this one was well documented.
-----For instance the same Yogi told a story of how his Master in old age, left his own body on the banks of the Ganga and took the dead body of a recently dead young man floating down the river.------
If this kind of control could be pushed to it's upmost, I mean REALY pushed, like the imagination (and gulability
perhaps) of some of you will have to be, then it could be quite possible for a person to control the programing of there own cells.
This is not considering the possibility of the light body, many storys have been told about this, like the one from the biography of Milarepa when He came to make multipul copies of Himself and stand them in a cirlce around somebody (I think?) but the truth is at this stage He didn't realy even have one physical form, He was in complete control over Himslef in all repects, He could have appeared as a cat or a mouse if it would have served His perpose, or simply vanished all together, this could probably be said closest to His acctual 'bodily' form. Also Jesus is of a similar..... state perhaps, He obviously has never died, that is if you beleive He has appeared to His Disciples in whatever times they've lived, like St. Francis I think in the 11th. century and Ramakrishna in the 1800's, It's just that He hasn't kept this form constantly on earth sense His "death" though quite possibly could.
But to acctualy answer the queastion there is an essay about Babaji at
http://www.alchemywebsite.com/ though I cannot find it now, I hope it's still there. There have also been a number of people that have clamed to have had Babaji's Darshan, one I have more faith in than the others, Swami Sivananda Radha, a Disciple of Sri Swami Sivananda Saraswati Maharaj.