For his part, Warren Buffett is concerned about Berkshire Hathaway's potential underperformance under his watch.

At the beginning of Berkshire's 2012 annual shareholder letter, Buffett lamented an underperformance of Berkshire's book value growth relative the S&P 500. He fears the firm's five-year book value growth rate may underperform the S&P 500 for the first time ever.

"To date, we've never had a five-year period of underperformance, having managed 43 times to surpass the S&P over such a stretch. But the S&P has now had gains in each of the last four years, outpacing us over that period. If the market continues to advance in 2013, our streak of five year wins will end," Buffett wrote.

In 2012, Berkshire's book value per share increased 14.4%, behind the S&P 500's gains of more than 15%.

Were Berkshire to perform below Buffett's goal posts in 2013, he indicated considering a dividend for the conglomerate, however, shareholders generally dismiss the prospect of such a move.

Buffett's legacy is a hot topic heading into Berkshire Hathaway's annual shareholder meeting on May 4, given uncertainty surrounding a successor to run the conglomerate with a market capitalization approaching $270 billion.

"I think the succession question will be obviously front and center," said Thomas Russo, a partner at Gardner, Russo & Gardner in an April interview. "I gather there will be some commentary."

In late 2011, Buffett also said his son, Howard Buffett, will succeed him as a non-executive chairman of Berkshire to oversee a maintenance of the firm's values.

Less clear is who would be chief executive of Berkshire Hathaway. Currently, speculation centers on insurance unit head Ajit Jain, BNSF railroad CEO Matthew Rose, MidAmerican Energy CEO Greg Abel as leading candidates to be Buffett's successor.

Buffett has informed Berkshire Hathaway's board of directors of his successor.

Russo, the Berkshire investor, sees room for multiple job openings to replace Buffett, when the time comes. He expects up to four roles to fit the shoes of Buffett.

Gardner, Russo & Gardner is Berkshire's tenth largest shareholder with a stake of nearly $800 million in the company's Class A shares and over $200 million of Class B shares, according to Bloomberg data. Russo says Berkshire holding's represent about 11% of the firm's assets.

While succession and Berkshire Hathaway's performance as the conglomerate grows in size both stand out as uncertainties heading into the company's annual meeting, they also may eventually prove Buffett's greatness.

Buffett likely has many years left at the helm of Berkshire to cut acquisitions and fire his elephant M&A guns before he passes the reins to a successor. Unlike his hedge fund and mutual fund contemporaries, however, Buffett's track record will be tested long after he's left Berkshire.

-- Written by Antoine Gara in Omaha, Nebraska.

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