Actually the lifespan of humans hasn't increased more than a year or two in history. Medicine and hygiene just keeps people from dying as children, even a thousand years ago if you lived past your childhood years and didn't die in war you could be expected to make it pretty close to today's average lifespan.

There is only so much that common sense medicine, hygiene, and good food can do though, truly lengthening, and even perpetuating, the human lifespan is more than doable, but it will involve genetic manipulation, I.e., forced and controlled evolution.