Warren Buffett is seeking to reassure shareholders about how his Berkshire Hathaway Inc. will perform in the decades after he steps down or dies, but remains as vague as ever about succession plans.

And that means some followers of the 83-year-old billionaire’s huge insurance and investment company remain far from comforted by his words, and worry about how well Berkshire can thrive without him.

“I don’t know of any good examples of an iconic CEO like Buffett ever being successfully followed,” said Meyer Shields, an analyst with Keefe, Bruyette & Woods, Inc.

Examples from the last 15 years show how hard this can be.

Jeff Immelt, the CEO at General Electric Co., has been unable to get his company’s share price anywhere near the heights achieved by his predecessor Jack Welch. Steve Ballmer had similar problems following Bill Gates at the helm of Microsoft Corp.

And after a strong start in following the iconic Steve Jobs, Apple Inc. CEO Tim Cook has had some major struggles in the past 18 months and the company’s share price is well off its highs.

One problem for any successor is that Buffett, by dint of his long stewardship of Berkshire and the outperformance he has delivered over most of the past half century, has the freedom to make mistakes or underperform the stock market in ways that could cost other CEOs their jobs.

“I feel sorry for the person who follows in his shoes,” said Dave Sather, president at Sather Financial Group, which invests more than 5 percent of its $365 million of assets under management in Berkshire.

“Buffett’s in a very unique position… to where he can just think 100 percent independently. I worry that the next person will not have quite the same flexibility to be a dealmaker.”

Certainly, Buffett’s profitable deal-making has been a boon to Berkshire for decades, and has at times been transformative for the company.

In his annual letter to shareholders this weekend, Buffett noted that Berkshire’s performance trailed the Standard & Poor’s 500 in 2013 – and in fact, even on a five-year basis it lagged that benchmark for the first time under Buffett. Berkshire’s net worth per share rose about 91 percent in the five years, while the index gained about 128 percent.

Still, since 1965, Berkshire’s book value per share has risen to $134,973 from $19. The nearly 20 percent annualized gain is twice the rate of growth in the S&P 500.

Buffett has said that Berkshire is likelier to outperform the S&P when markets are weak or moderate, in contrast to the surge in equities last year. While it lagged over the last five years, it has outperformed over the last six, including during the 2008 financial crisis.

SPLITTING ROLES

Berkshire plans eventually to split Buffett’s three roles as CEO, chief investment officer and chairman. The only one of those positions where succession has been clearly flagged is the last: Berkshire plans to make his son Howard non-executive chairman.

Berkshire’s board had previously identified three internal candidates for the CEO job, though it has never named any of them, with one of those selected to take over immediately in an emergency.

But in a regulatory filing on Monday, Berkshire eliminated its previous statement about the number of candidates and said only that “certain current” managers of subsidiaries were CEO candidates.

Speculation over succession has mounted in recent years, including after Buffett underwent radiation therapy treatments for prostate cancer in 2012.

Buffett on Saturday praised some of the people who investors believe could be among his potential successors – including Ajit Jain (the head of his insurance operations), Greg Abel (the chief of his power utility MidAmerican), and Matthew Rose (who leads his railroad company BNSF).

He also pointed out that portfolio managers Todd Combs and Ted Weschler – who could be candidates for the chief investment officer job – had outperformed not only Berkshire’s returns but those of the S&P 500 last year, though their portfolios of more than $7 billion each are small compared with the massive one that Buffett himself oversees.

The strong bench may not mean a lot in the days immediately after Buffett disappears from the scene, investors say.

“When he’s gone the stock price will probably get hit a little bit, 10 percent, 20, I don’t know,” said Paul Lountzis, president of Lountzis Asset Management in Wyomissing, Pennsylvania. Still, he said, such a decline would be “a great buying opportunity.” He cites the quality of Berkshire’s assets and the teams Buffett has put in place at various subsidiary units.

Lountzis invests more than 15 percent of his roughly $100 million of assets under management in Berkshire.

Not that Buffett isn’t preparing for the days when he isn’t around.

In the annual letter, Buffett said Berkshire is thinking a century ahead when the Omaha, Nebraska-based company makes big acquisitions now.

Last year, he bought half of ketchup maker H.J. Heinz Co. for $12.25 billion and Nevada utility NV Energy for $5.6 billion last year, to complement the more than 80 Berkshire businesses in areas from insurance to ice cream.

Heinz and NV Energy are companies that “fit us well and will be prospering a century from now,” Buffett said.

He also said the BNSF railroad and MidAmerican Energy units “will still be playing major roles in our economy” when the year 2114 rolls around, while “insurance will concomitantly be essential for both businesses and individuals – and no company brings greater human and financial resources to that business than Berkshire.”

Some investors point out that Buffett has shifted Berkshire more toward operating companies that pile up money, adding security for the future.

“He literally has built a perpetual cash generating machine,” said David Rolfe, chief investment officer at Wedgewood Partners Inc in St. Louis, which invests 9 percent of its $7 billion of assets under management in Berkshire.

Buffett did drop one small hint about his eventual departure, buried in a discussion of accounting practices.

Speaking about certain charges, Buffett said the full amortization “usually takes 15 years and – alas – it will be my successor whose reported earnings get the benefit of their expiration.”

Buffett would be 98 by then.

(Reporting by Luciana Lopez and Jonathan Stempel; Editing by Jennifer Ablan and Martin Howell)