Entrepreneur has not specific age of retirement. As an entrepreneur you retire when you feel it's convenient for you and most importantly when you know that business is well stabilized and nothing can happen to it at your absence. Then you can determine when to go and rest.I think it depends on the mental and physical well-being of the entrepreneur if you are still mentally or physically Fit at the age of 70 you can still run your day to day business if not then I think no matter your age you should retire.