66 in in fact quite old, many many many people die way before they get to 66 years old... very very few live past 66.

A majority of people live beyond 66.

https://www.ssa.gov/oact/STATS/table4c6.html#fn2

It’d be difficult to arrive at a life expectancy figure of 78 if a majority were dying before 66. To balance that you’d need a minority of Methuselahs, and the average life expectancy at 60 drops below 20. Even assuming a simple majority of 11 out of 20, with those 11 dying at 65, the remaining 9 will need to average 94 at death to make this work and that’s a rare age.