overall I feel better than I have in a long time
Probably because you feel relaxed after exercising ..
Constant heavy exercise is a lot of work. I think there is evidence that if you work out too much you may actually shorten your life span or cause stress injuries such as joggers knee problems etc, although you may be strong in the meantime up until then.
I tend to think moderate exercise is easier to maintain and is less time consuming. I have had a number of injuries over the last few summers but this summer I have been doing a bit more. This week I either walked for 45 minutes every day or rode my bike for 45 minutes or both. Sometimes doubling up in a day is good. On the weekend I try to hike for at least and hour and a half or a bit over 2 hours.
Surfing has been the best heavier type of workout.
The winter is the most challenging but I try to do some kung fu at a local place and stay as active as I can outdoors.
If my knees or feet are sore I try to take extra vitamins and supplements of all kinds.