I just read an uplifting post by James Altucher giving a brief rundown of late comedian Rodney Dangerfield. Often you find people as young as 35 bemoaning the "fact" that it's too late to get out of the rut they're in. Usually this rut is career related. People tend to settle down into unfullfiling careers and resign to this as their fate way too prematurely.
Yet here is a man who changed careers aged 48. He went from aluminium siding salesman to one of the world's best known comedians. Remember that even aged 40 you're still 25 years away from retirement age. Harland Sanders founded KFC in his sixties; Ray Croc was in his forties when he began franchising McDonald's. As long as your mind is fresh and body able, it truly is never too late to change careers. The number 65 is more of a psychological barrier than anything else. A 65 year old can have a mind as sharp as someone 30 years their junior. We all age at different rates. Read the story of Rodney Dangerfield here.