At 71, I don't want to "dial it back" - instead I have found a riding style, mode and frequency that suits my goals for where I am in life. That is different from what I did and my goals when I started at 58. Certainly my riding style and goals do not include how fast and far I can go. Instead, they include regular and frequent opportunities to ride my bicycle for enjoyment and fitness. Each of us finds our own "niche" for our particular time in life. I also do flexibility, resistance, and other cardio exercises such as swimming and walking.
I think you must find the answer to your own question consistent with your happiness, goals, fitness, etc. Fortunately, we are all different. YMMV