The idea of living many centuries is not new. It has been explored in fiction often, mostly fantasy and sci-fi. Tolkien’s ents, elves, and wizards live on for thousands of years, dwarves for several hundred, and those who posess the One Ring extend their years indefinitely. Merlin lives for centuries, in some accounts backward in time, Paul Atreides gains a near-immortality as God-Emperor, and various cyborgs and augmented persons travel here and there about the universes of speculative fiction.
Aubrey de Gray has brought it all front-and-center, suggesting that life extension is no longer out of reach. In our usual chronocentric arrogance, we believe this is all new territory. There are innumerable technical discussions and observations, but the philosophical discussions seem to be brief, and not very interesting.
A: I don’t know as I’d want to live to be 150.
B: Yeah, but you might if you had your health.
Or the quasi-theological discussion
A: I’m not sure that it’s right
B: Yeah, you religious guys say that about everything. It’s fine. Get out of our way.
(Aside: I know all you tech freaks out there believe you have thought it out more, and have much better arguments than this, but you don’t, really. You speculate on how it might affect society, or economics, or medical insurance. Related items, all quite interesting. Not on point. See my earlier post Your New Masters Will Have Asperger's.)
It is wise to remember that others may have wisdom. We won’t know how the individual will respond to life extension until we run the experiment, but as a thought-experiment, we don’t have any significant advantage in our era over those who pondered this a hundred or more years ago.
Earlier thinkers give perpetual life a mixed review. Old wizards may have their moments of cheer, but they’re a burdened lot with furrowed brow. Tolkien seems to have thought hardest about the possibilities, and illustrates a variety of responses. Bombadil and the elves are described as cheerful, celebrating creatures – but not vey convincingly. Gollum is tormented and miserable, perhaps because he was not designed for long life.
Emotional distance from the rest of mankind seems common to all these long-livers. Whether you are solitary in your long life or part of group, it is likely that those who will die soon and those who will die late will see themselves as separate. This is already how our hearts and minds work. Unless they are related by blood, the young and the old don’t have much to do with each other. A single generation is about all we can stretch for close friendship. Teachers see new faces come and go each year. They are fond of those they see for a time, but this seldom lasts.
Which leads to neglected speculation #1: If the 70 year-olds and 20 year-olds
don't have much interest in each other now, would they have much in common when they are 170 and 120? Many people elect to live a little longer. At any point you could drop in on even quite elderly people and ask "Die now, or wait a year or two?" For people still active and without major discomfort, a large number would clearly go on at each point of choice. Perhaps they would even go on farther than they ever thought they would want to.
But each year there are fewer and fewer people near them in age - and not necessarily the ones they would have preferred.
It looks like it should work better for those following, as they will be gradually prepared over their lives to live longer. But that second cohort has peculiar problems as well. I'll let you work your way back to that on the basis of the larger issue.
We were not designed to live indefinitely. Whether you believe we were created, evolved, or some synthesis of the two, the whole history of man has had mortality as one of its defining points. I am not sure I would want to cut myself off that fully from the entire history of humankind. What do literature and song mean when they no longer apply to you?