When Cathy Baron Tamraz, chief executive of Business Wire Inc., first read about Warren Buffett's management style, she wrote to the billionaire investor and asked him to buy her company.

And why not? As she said at the time, Mr. Buffett is renowned for his hands-off approach, which in turn generates loyalty -- and stability -- in the dozens of individual companies that make up Berkshire Hathaway Inc.

Berkshire bought Business Wire in 2006 and still owns it today. Ms. Baron Tamraz, who declined to comment, remains at the head of the company.

Mr. Buffett, who turned 83 in August, has outlined Berkshire's plan of succession at the top, although he has stopped short of naming his replacement as CEO. But some investors and analysts are beginning to think about whether Berkshire will remain such a desirable place to work for senior executives after Buffett turns over the reins.

'What happens post-Buffett. . .and there isn't anyone [the CEOs] need to make proud anymore?' asked Robert Miles, the author of a 2003 book on Berkshire CEOs.

Berkshire, based in Omaha, Neb., owns more than 70 companies, most of them headed by individuals who report to Mr. Buffett. Last year, more than two-thirds of Berkshire's pretax operating profit of about $20 billion came from subsidiaries other than its core insurance business. These units range in size from North America's second-largest freight railroad operator, BNSF Railway Co., to small Omaha-based trinkets supplier Oriental Trading Co.

Mr. Buffett has long relied on gut instinct to run Berkshire, eschewing bureaucracy and management layers that can hobble other large companies. He and his partner, 89-year-old Berkshire Vice Chairman Charles Munger, never tire of saying that they 'delegate almost to the point of abdication.'

Although it isn't unprecedented for Mr. Buffett to replace top executives, they typically leave only when they retire. Mr. Buffett, who declined to comment, has said that no manager of a significant Berkshire business has left voluntarily to join another business.

There has been more churn than usual at the subsidiaries lately. Last week, paint company Benjamin Moore named retail-industry veteran Michael Searles as CEO, the third person to occupy the post in two years.

Jewelry retailer Borsheims also named a new CEO last week after Susan Jacques, who had led the company since 1994, left for the top position at the Gemological Institute of America, a nonprofit.

'He's got very good people running the companies, and several down the line,' said Cliff Gallant, an analyst with Nomura. But 'retention is a risk factor. When he moves on, I'm concerned that some of them will move on.'

At a May gathering of Berkshire CEOs with Mr. Buffett ahead of the company's annual meeting, some managers asked him what their responsibility was after he was no longer at the company, according to people present.

Mr. Buffett encouraged them to preserve Berkshire's culture of autonomy, one person said.

People familiar with Mr. Buffett's thinking said the investor believes that Berkshire managers are loyal to the company and not to him personally. Still, he has acknowledged that despite his efforts to preserve Berkshire's culture for the future, things will change.

At the May annual meeting, Mr. Buffett said he expected his successor to reorganize the company 'modestly,' such as grouping the smaller businesses together. However, he added that the CEOs of the largest subsidiaries would likely continue operating their businesses as they do now.

Mr. Buffett has said his job will be divided into three when he leaves. The role of nonexecutive chairman will go to his son Howard Buffett, and his role as chief stock picker for Berkshire will be shared by two investment managers, Ted Weschler and Todd Combs, hired a couple of years ago. A third person will take the CEO mantle. Mr. Buffett has said Berkshire's board picked a candidate, but the name hasn't been revealed.

The challenge for a new CEO will be to maintain Berkshire's unique culture. Ajit Jain, who runs Berkshire's giant reinsurance business and has long been seen as a front-runner by Berkshire watchers, is very close to the billionaire investor and well-regarded by colleagues. However, little is known about Mr. Jain's management style or deal-making, as he has eschewed publicity.

The average age of the Berkshire chiefs is 59, higher than the 56.7 average for CEOs of companies in S&P 500 index, according to a Wall Street Journal analysis and data from Spencer Stuart, an executive-search firm.

One potential issue going forward: Berkshire's unusualcompensation model. While stock-based compensation made up 44% of the pay of CEOs at the largest U.S. public companies, Berkshire doesn't offer such awards. Instead, Mr. Buffett pays his executive bonuses in cash, part of which is tied to long-term performance targets, which aren't publicly disclosed.

Mr. Buffett, the world's fourth-richest man, with nearly all his net worth tied to Berkshire stock, has his annual salary fixed at $100,000. But compensation for most of his managers isn't disclosed. Some are paid handsomely: Geico Chief Executive Tony Nicely, utility company MidAmerican Energy Holdings CEO Greg Abel and BNSF chief Matt Rose are among Berkshire managers paid in the millions annually, according to analysts.

Mr. Buffett has long held that letting managers run their businesses for the long term rather than switching out CEOs every few years is key to creating institutional values and preserving them.

Part of that long-term planning has involved the Omaha native asking for regular succession plan updates from his managers. In 2010, he disclosed a memo he sends to his 'all stars' every two years, asking for their 'recommendation as who should take over tomorrow if you should become incapacitated overnight.'

Some shareholders are bracing for change.