The ultimate American dream used to be to get rich young and "retire by 40." Now the goal for the rich is to retire past 70—if they retire at all.
A new survey shows that America's highest earners don't plan on retiring until they are at least 70 years old. Lower-income groups—and even those considered "affluent"—plan to retire much younger, according to the study from Spectrem Group, a wealth research firm.
When asked "At what age do you expect to retire?" nearly one-third of those with annual earnings of $750,000 or more answered "over 70." Fifteen percent of them say they never plan to retire.
(Read more: What is rich? Study takes a crack at the answer)
On the other hand, only 6 percent of those making under $100,000 a year plan to retire after 70, and the same percentage say they never plan to retire. Most plan to retire by 65.
The Spectrem survey is backed up by other, previous studies. A 2010 study from Barclay's Wealth found that 54 percent of millionaires say they want to continue working in retirement. Globally, 60 percent of those with a net worth of $15 million or more plan to stay involved with work "no matter what their age."
The numbers contrast with the popular notion that Americans are retiring later mainly because they can't afford to stop working. The Spectrem survey shows that the highest earners—and those who can best afford to retire—are actually working the longest.
Many of the respondents earnings $750,000 or more are business owners and entrepreneurs. They are far more likely to take risk in their finances and their life, and they are more likely than those with lower incomes to credit hard work for their success.
George Walper, president of Spectrem, said there are two broad reasons for the retirement-denial of the rich. First, he said, many of them own businesses that they cannot easily leave. If they retire, the business fails—so they have little choice but to keep working until they have a succession plan or buyer.
(Read more:Ultrawealthy investors turn bullish on stocks)
But he said the main reason is that entrepreneurs love their work and can't imagine life without it.
"Most of these people enjoy working and are very involved in their businesses," Walper said. "To them it isn't really work." For those in lower-income brackets, he said, "a job is a job—it's a more traditional experience."
Corporate America is now filled with founders over 70 who are still active in their companies or in business—from David H. Murdock, the 90-year-old CEO of Dole Food who is trying to take the company private) to the 90-year old Sumner Redstone at Viacom and the 71-year-old casino tycoon Steve Wynn.
(Read more:Billionaire Carlos Slim: Why 60 is the new 30)
Walper added that even among top earners who say they're "retired," many continue to serve on boards, advise their companies or work the phones several hours a day. They also may be doing more of their business from a more pleasant spot—say, their pool in Palm Beach—rather than a corner office.
"They may say they're retired because they're only working five days a week now instead of seven. And they're doing it from a different location," Walper said. "To them, that's retirement."