People live significantly longer now than they did in the 1700's. Lower infant mortality rate/fewer incurable diseases/healthier diet/better meds.How long will they live in 300 years?

 People now die in their 80's or 90's or even older.  Many live for a very long time. Not so a few hundred years ago. The Founding Fathers foresaw a lot of things that could be potentially harmful and tried to take precautions to counteract them. They did not foresee how long people would live.