Never. Most people I know who retire die within 2 or 3 years. Keep working and take long vacations, but have a job when you come back. Sleeping to 9 - 10 o'clock in the morning is not healthy especially when you get older. You got to keep moving and keep that blood circulating. Unless you are loaded to the gills and can afford to continually travel around the world, you might just keep on working as long as you can.