How long do you think you'll be around for? Ninety years? One hundred and twenty? Aubrey de Grey, a biogerontologist and Cambridge-trained Ph.D. who studies aging, thinks we could engineer techniques that reverse the wear on our bodies by replacing lost cells in our bones and hearts and even tweaking the cells themselves to prevent their degeneration. If de Grey is right, these therapies could help us live for hundreds-if not thousands-of years. What would we do with all that time?GOOD:How can we slow down aging?AUBREY DE GREY: In my view, we probably can't slow it down much at all. All we can do is reverse it. Yes, I know it seems paradoxical that reversal would be easier than slowing, but if you think about it, that's what we do with simple manmade machines such as cars or airplanes: We do periodic repair and maintenance. That's how we'll delay the ill health that aging eventually causes.G: So with the therapies you're talking about, would the whole development process take longer, or would we mature to adulthood in 20-odd years and then stay in that state for hundreds more?AD: The latter. Development and aging are two different processes. Development is a programmed process that essentially ends around age 20. Aging is an unprogrammed process that happens throughout life, and it's one we can affect.G: When you say we can reverse aging, what does that feel and look like? Does our skin get less wrinkly? Do our bones get stronger? Do we get shorter? Taller?AD: Yes, yes, no, no. We are restored to the look, feel, and function of a young adult.G: How would living for hundreds of years affect how we use our time?AD:It's impossible to say for sure, but I think the changes would actually be rather slight. We don't make career or life choices today in early adulthood on the basis of only having 50 more years to live.G:One thing people sometimes lament about modern life is the hectic pace. We don't seem to have time for leisurely walks or meals with the family or quiet reflection. With more time to live, would we reconsider the value of down time?AD: I think we will-not so much because we will expect a longer life, [but] because our other technology will continue to improve and give us the option of more leisure.G:Have you seen Groundhog Day? Will we all end up like Bill Murray, using our time to learn how to play new instruments and make ice sculptures, eventually reaching a place of Zen selflessness?AD: I haven't seen it, no. I find that essentially all fiction relating to the defeat of aging incorporates some arbitrary negative aspect for no reason at all, other than to make people feel okay with the fact that aging exists. But sure, I think we will get progressively more out of the creative and altruistic aspects of life.G: I know you've heard this question before, but wouldn't living for hundreds of years get a little boring?AD: Yeah, right. Wouldn't it be so terribly boring not getting Alzheimer's? At least you had the sense to be embarrassed at even asking the question.G: I didn't mean to suggest that the maladies of old age are what keep life exciting. But it does seem like we're propelled through life by milestones like moving out, marriage, having children, buying a house, and retiring. Isn't it possible that life becomes a little desultory without this normal rhythm?AD: I don't think so. We have been progressively shifting to doing things like that multiple times in our lives rather than only once, and that shift will merely continue. And it hasn't made life desultory so far, so I see no reason why it should do so in the future.G:How will we think about death differently? Will it seem even more tragic if it's not inevitable?AD: I think we will indeed be much more risk-averse, and we will address that by making our most risky activities less risky-by making cars safer and by investing more money in vaccine development, for example. But let's remember, I'm not working on eliminating death, only one cause of death.G: How long do you think you will live?AD: That depends on the pace of progress against aging. If progress is slow, probably between 90 and 100 [years]. If it's faster, there's no limit.G:What do you wish you had more time for these days?AD: Sleep.