Nearly half of 600 wealthy U.S. business owners in a recent survey said they want to work until age 70, nearly double that of affluent Americans who do not own a business.

While 77 percent of the business owners surveyed had completed a will, only 33 percent had a succession plan in place for their businesses, according to PNC Wealth Management. Despite substantial retirement savings, many business owners said they wanted to continue working simply for the enjoyment of it. Indeed, the survey found business owners were more than twice as likely to work no matter how much money they had.

"Business owners who have put a lifetime into their work often have a mindset that 'no one can run this business better than I can," Jonathan Lander, vice president of PNC Wealth Management, said. "Many view their businesses as an extension of themselves and are unable to envision any one else in charge," Lander said.