Dear Ageless Traveler, I learned an unfamiliar word this week: "tsundoku". It means buying books you have no intention of reading. I used to do that—no more. When I buy books now, I read them to the end. That is one of many changes that have come about as I age. I no longer have the money or the time to pursue that in which I am not interested. Also, what I read now has changed, like this article on peptides. Healthspan is the central theme in this week's podcast on longevity. Let's put the...