I'd put over/under at about 65 for me, though I don't go to great lengths to keep them alive. I usually try to have a kid when the parents are 48 or so, and usually they go off to college about the time that the parents die. I have had an 8 year old orphan, though. If you keep them well fed and healthy, giving them vitamins, fresh fruit, and organic food, you should get them well into the 70s a lot.