I'm firmly in the "old fart" category. For me, cycling is a two-fold activity - the sheer pleasure of being out in nature on two wheels (which is my main driving motivator), and the ability to help keep the Michelin man at bay by getting the heart rate up. I am not and have never been a competitive cyclist, so I'm never riding to "train". That being said, I would much rather gear my rides toward enjoyment and ride them as hard as my body and mind want to let me, knowing that the caloric balance sheet will likely end up in my favor. If I'm out of breath at the end of a climb, I did it right. If I'm not, I ride harder on the next one. I ride a fatbike 24/7, so the former is usually the most common denominator. I have 2 kids, 12 and 8, so about 2 hours (including driving to the local trailhead) is about the timeline of what my rides are by necessity compacted into. I would love to have the ability to do multi-day bikebacking runs, but kids/family (for now) dictate otherwise.