Interesting topic. In recent years I've also begun to wonder about the "Yoda" stereotype of the ancient martial arts master enjoying surprising longevity and health that belie his years. I've begun to doubt the positive value of some conditioning practices ...as I have begun to feel their adverse effects. And, aside from the negative effects of inflammation from hard training, conditioning exercises and sparring, what about the cumulative long-term effects of taking shots to the head during sparring? All the recent evidence of the effects of concussions is worth thinking about.
I hear a lot from some people about the necessity of being able to "take a hit", and to frequently spar with heavy contact. That may well be necessary to be a competitve fighter, but the science is increasingly clear about the risks involved. As I'm getting on a bit (I'm now 58) I feel that personally the cost of such training outweights the benefits. As it is I get injured more and more frequently, take forever to heal, I hobble around like a cripple, and hurt most of the time. So I'm by necessity resolving to focus on the gentler side of the arts I train. Eventually we all must pay for the excesses of our youth.