I retired in April @65 and I am trying to regain some of the fitness I lost over the last 2 years due to work interfering with my riding. I've always done seat of the pants type training and never used any electronics and have until the last 2 years done around 5-6000 miles and 300,000 feet of climbing, or so.
Now I have time to ride all I want but I have been tending to overdo it. I feel stronger so I go harder, trying to keep up with faster riders and it wipes me out the next day. Have not yet been able to get back the endurance that used to be my strong point.
Oh, and a lot of us wish we could ride with jppe.