What a dream retirement plan looks like for 12 of the richest CEOs in America

Net worth: $78 billion

Forbes 400 ranking: #3

"If I quit today — I see these people. They spend a whole week planning their haircut. That is not my idea of living," Buffett once said, adding that it would be "crazy" for him to leave his job. "I would rather do this than anything in the world."

At 87 years old, Buffett is still steering the helm of Berkshire Hathaway. If you love what you do as much as he does, know there are a few benefits to sticking with your work.

Research shows that retiring at the age of eligibility has a detrimental effect on cognitive ability. Working even a year beyond retirement age have a significantly lower mortality rate.

Net worth: $23.2 billion

Forbes 400 ranking: #14

"I think being 50 years old and being in good health, [retirement and succession] is not a likely scenario anytime soon," Dell told Economic Times in 2015. "I'm having a good time, the business is doing well, can't do it forever, but it's working well and we don't have a problem."

While some dream of an early retirement, others dream of prolonging it. If you're happy and thriving in your career, there's no reason to hang up your skates early — and when you do, you'll rest easier knowing that you spent more time building your wealth and collecting social security.

If you delay retirement past full retirement age (up to age 70), you can qualify for delayed requirement credits that increase the value of your social security payments by 8% for every year you wait.

Net worth: $20.8 billion

Forbes 400 ranking: #21

"It would be a good place to retire," Musk once told The Guardian. It, of course, is Mars, the planet Musk is hoping to colonize with one million people via Space X.

By the time you retire, Musk may have made this goal a reality and you, too, can spend the rest of your days on Mars.

If not, there's still an important takeaway: dream big and live adventurously. Consider purchasing a second home in an exotic locale to leisurely while away your sunny days of retirement.

Net worth: $13 billion

Forbes 400 ranking: #34

Speaking of his father, who retired young, Cohen told Fortune magazine, "I can't imagine myself retiring the way he did — not that I'm ever going to retire," explaining that it pained him to watch his dad squander away vital years with little activity or purpose.

People are working longer not because they have to, but because they want to. The Pew Research Center reveals that as of May 2016, 18.8% Americans aged 65 and up were still working — a 5%-plus increase since 2000. That number is expected to increase to 32% over the next five years.

When you do retire, you can still continue activity and have a sense of purpose with a part-time job. Transamerica Center for Retirement Studies found that 56% of US workers intend to take on part-time work after they retire.

Net worth: 9.6 billion

Forbes 400 ranking: #48

Koum took a year off after leaving Yahoo to travel — a sort of mini-retirement, if you will.

"Ever since I semi-retired a little over a year ago, I [have] been traveling A LOT, and I hated it when people tried to reach me when I am on the plane out of the country" Koum once wrote in a forum. Soon after, WhatsApp was born.

Some Americans are embracing shorter periods of reflection, travel, or activities with shorter periods of work. Changing the way you think about retirement by interspersing it throughout your life in lieu of one big chunk at the end may better fit your lifestyle and set you up for more success like Koum.

Net worth: $3.8 billion

Forbes 400 ranking: #186

"[When I retire], I'd like to say that Airbnb created 100 million new entrepreneurs in the world," Chesky told The New York Times.

While approaching retirement, don't forget about how you want to be remembered and what you want to leave behind. In your career, that might mean implementing a new system or leadership program; in retirement, that could be creating a foundation or donating to charity; in your personal life, that usually involves leaving behind an inheritance for your family.

For the latter, make sure to build a robust estate plan — not doing so is one of the biggest retirement saving mistakes people make.

Net worth: $3.4 billion

Forbes 400 ranking: #219

"I never had any personal desire to be a wealthy billionaire living lavishly. My estate plan has the money from my Epic shares going into a foundation," writes Faulkner in her letter to the Giving Pledge.

"Many years ago I asked my young children what two things they needed from their parents. They said 'food and money.' I told them 'roots and wings.' My goal in pledging 99% of my assets to philanthropy is to help others with roots — food, warmth, shelter, health care, education — so they too can have wings," she wrote.

The healthcare innovator is not the first billionaire to commit to the Giving Pledge, but she is among those donating the most money. Needless to say, her retirement will be one of giving and living simply.

While it's important to save enough for retirement so you don't go broke, your idea of retirement doesn't have to equate to a bigger house or a luxurious lifestyle. Some retirees prefer a simpler lifestyle and opt to downsize.

Considering that a baby boomer retiring today at age 67 with $1 million in savings generates an average annual withdrawal of only $40,000, the simple life isn't a bad idea.

Net worth: $3 billion

Forbes 400 ranking: #264

Real estate mogul Perez is grooming his sons to take over Related Group. "They'll keep on earning their place in the company, and of course my hope would be that they would come to run the company a few years from now," he told Bloomberg. "I can act much more as sort of the true chairman of the company and do some of the things I want do," adding that he'd like to focus more on travel, philanthropy, and art.

Come retirement, you'll have a lot of time on your hands. Now is the time to explore your interests to the fullest extent — play golf more, start a book club, or travel the world. Some 70% of retirees say that traveling has helped them enjoy life.

Net worth: $3 billion

Forbes 400 ranking: #264

"After careful consideration, we are delighted to join in Sacramento's bid for Major League Soccer," Whitman and husband Griffith Harsh said in a statement two months before her retirement from Hewlett Packard. "Sacramento has proven itself a great soccer destination worthy of entry into MLS."

Retirement is a great time to support and give back to your community. While you may not have the means to offer as extensive support as Whitman, consider teaching or mentoring, joining a local board, or volunteering at a local business or charity. Many retirees find giving back to be fulfilling.

Net worth: $2.9 billion

Forbes 400 ranking: #278

"I don't see any scenario where I am not working hard, pushing it," Rubin told Entrepreneur.com when he was 41, adding that retirement wasn't on his mind. "I am not very good at relaxing. Relaxing is not a core strength of mine. Somebody said to me a couple days ago that they were curious if I slept. It's not something I really enjoy doing."

Rubin is all about the hustle — if you are, too, consider cultivating one of your hobbies into a little business during retirement so you can make some side cash. You'll still have the benefits of being retired while putting in as much effort as you like.

Net worth: $2.2 billion

Forbes 400 ranking: #359

In 2011, the man running your most recent binge-watch told Business Insider, "I can certainly say that I'm not thinking of retirement this year, but ten years for anyone, it can depend on so many things."

Hastings is right; retiring, especially if you plan to do so early, depends on many factors. According to Business Insider's Lauren Lyons Cole, the essential variable is your lifestyle — namely, your spending habits now and in the future. This guideline will help keep your savings on track at every age.