Pity the put-upon CEOs. Let us count their burdens:

Heavy expectations from impatient boards of directors. Intensified pressure from shareholders, unions and competitors. Onerous scrutiny from regulators. And zero job security.

The tenure of chief executives, those richly compensated princes riding herd on America's publicly traded companies, ranks among the shortest of any professional group. And it's continuing to be whittled down, according to recent data from consulting firms.

Forty percent last no more than two years in the corner office. The average CEO's tenure dropped from 9.7 years in 1999 to 8.3 years in 2006, the most recent year for which statistics were compiled by consultants Challenger, Gray & Christmas, Crist Associates, and Spencer Stuart. The median tenure —- the number separating departures on the higher and lower halves —- stood at 5 1/2 years in 2006.

Remember the gold watches presented at retirement parties for decades of devoted service? The most fitting gift for CEOs heading out the door today might as well be a gilded boot.

"You have only one chance to get it right," warned Mark Gottfredson, a partner in the Dallas office of management consulting firm Bain & Co., who's analyzed CEO turnover trends as disruptive technology and globalization have scrambled the game over the past decade. "And if you don't, you're out on your bum."

Not that the penalty for being bounced is too harsh. Robert Nardelli walked away from Home Depot Inc. with a $207 million severance package last year after failing to lift the company's sagging share price. Nardelli, a protege of Jack Welch at General Electric Co., was quickly snapped up to run automaker Chrysler Corp.

Carly Fiorina, who engineered technology giant Hewlett-Packard Co.'s controversial takeover of Compaq Corp. in 2002, was canned three years later by a disenchanted board.

Despite the cushioned landing, there's no shortage of advice for chief executives who'd rather stay in the saddle a bit longer —- and maybe enrich their investors as well as their bank accounts. Gottfredson and Steve Schaubert, a Bain partner in Boston, last month published "The Breakthrough Imperative," a kind of how-to-succeed book for new CEOs.

They recommend sizing up a company's prospects and crafting a winning strategy in alignment with "four laws" they'd earlier laid out in a Harvard Business Review essay: Costs and prices will decline over the long term. Competitive position will determine your options. Profit pools will be constantly in flux. And customers will reward simplicity.

"You've got 90 to 100 days to do a diagnostic on your point of departure," Gottfredson said. "You've got another 30 days to turn that into a compelling, motivating, realistic vision for the point of arrival. Then you've got to have a path for getting from Point A to Point B."

That's four months to take stock and design a road map, and an additional year at most to wrestle the enterprise onto the right track.

But executing is far from simple in today's business world, where a turnaround plan has to encompass everything from product innovation and market segmentation to technology shifts and changing customer tastes.

"All of the warts, all of the mistakes that used to be hidden in the past, are out there in the open today," maintained John A. Challenger, the chief executive of Challenger, Gray & Christmas, a Chicago outplacement firm that tracks CEO tenure. "Every time you make a bad decision, you get crucified. There's much less potential for a long-term tenure and more potential for an ignominious exit."

In many ways, the increasingly tenuous ties between boards and their hired guns is a reflection of trends in the broader society.

"Boards want to see results immediately," said Lauren Mackler, an executive coach and corporate consultant. "That's not the best way for a new CEO to acclimate into an organization. If you come in with a machete and produce fear, you're not going to get the results from people that you want to have."