Billionaire investor Warren Buffett used his widely-read annual letter to Berkshire Hathaway Inc. shareholders on Saturday to again call out the wasteful fees that many money managers charge. He highlighted the risk of bonds and emphasized the importance of sticking with a simple investment strategy, rather than chasing returns.

“Performance comes, performance goes,” Buffett wrote. “Fees never falter.”

The letter, which was notably shorter than in years past, meditated on the investing lessons that the Berkshire chairman and chief executive officer thinks people should take away from his charitable bet against Protege Partners. Buffett challenged the asset manager to pick a group of hedge funds that it thought would beat an S&P 500 Index fund over 10 years. When the wager concluded on Dec. 31, the index fund had won easily.

Buffett urged investors to stick with stocks even though they can be riskier in the short-term.

“It is a terrible mistake for investors with long-term horizons — among them, pension funds, college endowments and savings-minded individuals — to measure their investment ‘risk’ by their portfolio’s ratio of bonds to stocks,” Buffett wrote. “Often, high-grade bonds in an investment portfolio increase its risk.”

He also spent much of the letter explaining Berkshire’s results for 2017, which were aided by a huge gain on the recent U.S. tax overhaul. The Omaha, Nebraska-based conglomerate’s insurance businesses, however, posted a rare underwriting loss.

He also discussed some of the challenges to finding large acquisitions. Cash has been piling up at Berkshire, but Buffett said most of the businesses he looked to buy last year were too expensive. The 87-year old reiterated that while he’s “never felt better,” the company has a succession plan in the works.

“Our directors know my recommendations,” he wrote. “All candidates currently work for or are available to Berkshire and are people in whom I have total confidence.”