Even if the author's arguments are true, the book doesn't even try to explain the effects of oversleeping. We know it's associated with higher mortality risk, j

Even if the author's arguments are true, the book doesn't even try to explain the effects of oversleeping. We know it's associated with higher mortality risk, just like insufficient sleep. But the author conveniently ignores this fact and advises everybody to sleep for at least 8 hours.