Berkshire’s stock price recently reached a new all-time high, giving Duan Yongping a rare moment to savor vindication. He once shared a widely known piece of investment advice: if you’re not very familiar with the U.S. stock market, consider investing half your money in the S&P 500 and the other half in $BRK.B. The stock’s strong performance now has once again borne out the view he has long stood by.