I don't see the connection between the decrease in infant mortality and the increase in average life expectancy. I think it's mainly due to discoveries in the field of medicine, drugs and technology.
actually, maybe quite young looking. With genetic treatment that makes you younger not older. Already achieved on mice. But it will probably be only for millionaires.
edit: I should have said, for those who have at least a full bitcoin :)
Now imagine being 200 years old