Q: Why not go out and find better investments, as you did in the past?
A: When I was 35, I had lots of time and less money, so doing 10% or so better than the index, with little risk, was attractive and fun. At 85, the marginal value of time is higher and the marginal value of money is lower. These are strong disincentives when I can make a long-run 10% or so by doing nothing. Q: You’re 85 and look like you’re in your early 60s. What’s your secret? A: I think rationally and clearly about how to slow aging. I’ve been exercising since my 20s. I started running marathons when I was 47. I’ve run 22; my personal lifetime best is 3.17 hours. I spend five hours a week in vigorous walking or easy jogging. I work out with a trainer twice a week. I feel I should do more. I have a body-mass index of 22 and am comfortable there. I try to eat semi-intelligently. I have never smoked. It has got to be one of the stupidest things. I have never met Jim Simons of Renaissance, the greatest quant hedge fund guy ever, because he was a chain smoker and I didn’t want to go into his office. You should think about your overall health and fitness plan. You are your own best health manager. Get started by telling yourself: Some is better than none, and more is better than less.