You've set yourself up for eventual failure by planning to ride farther and farther the older you get. You're obviously tremendously fit or you wouldn't be able to ride 100 plus miles at 62 years old, but you're only human; as people get older they generally, eventually become less able to meet great physical challenges. Maybe that's why you've lost some of your drive - you're facing your own mortality.
Also, regular nights of 4 and a half hours of sleep is way too little for good mental and physical functioning. Why are you driving yourself so hard?