30-40 min is a long time but you are loose for the rest of the day? I am thinking about something low impact like tai chi or yoga to build up my core and stay flexible. I notice that having stronger muscle help with posture a great deal. As we get older, we stop doing the heavy lifting and sit a bit causing what I call lazy muscles. Getting a small tire around the waist and it hinders climbing. I hate climbing BTW. Anything over 50 miles is starting to hurt. Our sat ride is exactly 46 miles of trying to kill each other with no wait until the finish. the rest is riding back to the car. anything over 60 is just too long a day in the saddle.
I am like your friend, want to get on with the ride and hate riding at 12 mph talking, looking at birds or stopping for coffee. That's why I don't do much of those centuries but I do have fun going up to Northern CA doing the Levi ride. That ride kicks my ass. I cramp badly each and every time. Already registered for the next due to peer pressure from this group. They are lots of fun.
There are lots of really fast 50 year old out there like your friend because they have time to train and know their bodies well from years of riding. They just know how to ride and know when and where to hit you where it hurts. I hate those guys
