Wisdom of the aged is enough to keep investors toeing line. (Commentary).

LET'S hear it for septuagenarian CEOs. Saudi Prince Alwaleed bin Talal, the biggest shareholder in Citigroup Inc., said in mid-April that Sanford Weill, 70, deserved to remain boss of the financial services company for "another 10 years."

Alwaleed, who owns 5.17 percent of Citigroup shares, a stake worth more than $10 billion, said Weill belonged in them same class as Maurice "Hank" Greenberg, who, at 78, still runs American International Group Inc., the world's largest insurer.

Weill and Greenberg needed no encouragement from Alwaleed, who's only 46. Aided by sheer willpower or weak-kneed directors, the CEOs show no sign of retiring -- or of even naming a successor.

Citigroup's growth-by-one-acquisition-atop-another strategy is suspect, but Alwaleed liked the 18 percent gain reported by Weill for the first quarter. MG had a rare loss in the fourth quarter of 2002 but was back on track this year after raising its prices.

Weill and Greenberg aren't the only old-timers who remain in charge after what would seem to be their prime. Warren Buffett, 72, will run his Berkshire Hathaway Inc. conglomerate until he drops. Martin Whitman, 78, manages the $2.2 billion Third Avenue Value Fund -- and got good marks during the recent stock decline.

J. Willard Marriott Jr., 71, heads the hotel chain that bears his name. Two years ago, Corning Inc. brought back retired Chief Executive James Houghton, now 67, in an attempt to rescue the stumbling fiber-optic-cable maker.

And in late April, President Bush said Alan Greenspan, 77, deserved another four-year term, starting next year, as chairman of the most important economic enterprise of all: the Federal Reserve. Greenspan said he was willing.

Old geezers seem particularly prevalent in the entertainment business. At 80, Summer Redstone is still king of Viacom Inc., which owns CBS and MTV. Rupert Murdoch, 72, remains in control of News Corp. Ralph Roberts, 83, is active as a director at Comcast Corp., the biggest U.S. cable TV company, now run by his son Brian.

Redstone, Murdoch and the elder Roberts are still around for the obvious reason that each controls the votes of his corporation. Redstone has a perfect successor in President Mel Karmazin, 20 years his junior. Karmazin ran CBS before it merged with Viacom in 2000, and many investors would like him to take over now. That fact no doubt has increased tension between Redstone and Karmazin, both of whom knew they'd have trouble getting along from the outset.

Buffett is in charge, too; he controls 35 percent of Berkshire's votes. The company's board meetings are a veritable gathering of geezers. Six of the nine are 70 or older, including Vice Chairman Charles Munger, 79, and the two latest additions, ex-Coca-Cola Co. President Donald Keough, 76, and 77-year-old Thomas Murphy, once head of Capital Cities/ABC Inc.

None of Buffett's adoring shareholders want him to leave, however. And he at least has a succession plan. He says he always has in mind two people to take his place: one to run Berkshire's many businesses and the other to oversee investments. That's either very practical -- considering the company's growth and performance -- or egotistical.

Alwaleed was right to say CEOs shouldn't be discarded just because they're old. Seventy-five doesn't mean senile, and mandatory retirement at 65 seems silly in an era of medical wonders. (Full disclosure: The writer is 67.) So stick around, guys. Just don't start thinking you're indispensable.

David Pauly is a columnist with Bloomberg News.