I think every person should retire whenever he feel like doing it. Its depends on a job of course. For example people who work on hazardous or dangerous jobs like some chemical production or military have to retire earlier. But there are many people who are full of energy even at 70 and they dont want to retire. For some people job is meaning of life. If they are single they have nothing to do at all exept their work and if they loose it their existance getting pointless and lonely. So there is no exact retirement age.