I was just reading an article about a way life expectancy could be extended enormously, to well over 1000 years in humans.
With a way to almost cure ageing being theorised, would you like it to be done for you? Would you like your aging process to be reduced so that you could live until you were 3000 years old? What would you do with all that time on your hands?
I think this would certainly lead to the earth being way overcrowded, so it would have to be done selectively if it works. But it's really an interesting topic
http://news.bbc.co.uk/1/hi/uk/4003063.stm