I would qualify this a little. Buffett says his favorite holding period is forever, not his only holding period. He sells stocks from time to time for different reasons. Also, the trick is finding a company that you should hold forever. Notice Buffett doesn’t often get sucked into companies that flame out like Wirecard. So another way to look at this is that your friend didn’t really follow Buffett’s advice in full, which includes only buying great companies that you understand and that you should hold forever, but sell if you are wrong plus many other tidbits. Following only a small part of good advice is not the same as following good advice. In the end, the best advice is to just buy the S&P500. To do better is very difficult.