Approximately $155 billion of Berkshire Hathaway's $307 billion investment portfolio is currently put to work in three brand-name businesses.

The clock is ticking on what has been one of Wall Street's most-successful investing careers. In three months, billionaire Warren Buffett will step down from his role as CEO of Berkshire Hathaway ( BRK.A 0.70% ) ( BRK.B 0.71% ) -- a role he's held for the last 60 years -- and hand the reins over to predetermined successor Greg Abel.

There's little question the Oracle of Omaha's presence will be missed on a day-to-day basis as CEO. In his six decades as Berkshire's boss, he's overseen a cumulative return that's topped 6,000,000% for his company's Class A shares (BRK.A), as of the closing bell on Sept. 25. Riding Buffett's coattails h

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