Bill Gates' impending retirement gives new meaning to the advertising slogan "Retire rich." Still, at age 52, he needs to ensure not only that his $58 billion lasts but that his golden years are filled with meaningful pursuits. We asked some of Forbes.com's investment guru contributors for some free retirement advice for Gates. Below are some of their responses.

Jim Lowell, Forbes ETF Advisor; chief investment strategist, Advisor Investments

For the man who can literally have anything he wants but whose war chest is lopsided in favor of technology, I'd recommend my Ludite Growth Fund. My decidedly unplugged, anti-tech composites provide a complement to Bill's wired world.

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Bill Gates' fortune over the years
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My picks: the down-on-the-farm PowerShares DB Agriculture exchange-traded fund (DBA), made up of the most liquid and widely traded agriculture products Bill's consumers can't live without--corn, wheat, soybeans and sugar. The PowerShares Deutsche Bank G10 Currency Harvest (DBV) will let Bill benefit from the fact that on any given day interest rates are going up and down in one or more of the G10 markets.

And to keep Bill's wired world humming, I'd steep some Texas tea through the United States Oil Fund (USO) and mine coal, the dark heart and soulless fuel of global economic growth by way of the Van Eck Market Vectors Coal ETF (KOL).

Chuck Carlson, CEO Horizon Investment Services; editor, Drip Investor

Gates should position his money with Horizon Investment Services (my firm). We would set up an investment program that would match his unusually long retirement period (after all, he is retiring at just 52) with proper risk controls to ensure that he does not outlive his funds.

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Close friends' wishes for Bill Gates
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We would probably have to put him on some budget, of course. Assuming a normal 4%-per-year withdrawal rate, I think we could budget about $6.3 million per day, or around $4,375 per minute. I'm quite confident that should meet his and Melissa's spending needs.

Josh Wolfe, managing partner Lux Capital; editor, Forbes Wolfe Emerging Tech Report.

Two words: rational allocation. Warren Buffett, who vetted Bill's philanthropic plans, pledging his war chest to Gate's charitable crusades, once said you pay a high price for a cheery consensus. Thanks to Al Gore's global warming hysterics, the public sure is.

Gates would do well to rationally allocate his cash by the prescriptions of Bjorn Lomborg's Copenhagen Consensus--smartly weighing the costs and benefits of the world's biggest problems. And prudently parking the rest in the cash compounding machine that is Berkshire Hathaway would leave plenty of time to play bridge and plan the world's most expensive prank on Larry Ellison.

John Christy, editor of Forbes International Investment Report

Africa is the next big thing in emerging markets. But picking stocks there can be tough. For now, the real money is in private, hands-on investments on the ground.

Slideshow:
10 predictions from Bill Gates

Video:
Microsoft's uncertain future

Gates should start his own African venture capital/private equity fund. Why? At 52, he still has a long-time horizon to work with, so he needs some growth in his portfolio. At the same time, he's rich enough that he can take some risks that others might not be able to stomach. And because he's Bill Gates, he could attract a lot outside investors and top-notch expertise too.

Ultimately it dovetails with his charitable work too. His foundation is doing great work, but by providing capital, expertise and inspiration to a generation of African entrepreneurs--perhaps one may become the next Bill Gates--he'll have an even bigger impact on the region's economic development.

Curtis Hesler, editor, Professional Timing Service

Given that Bill will not have to worry about money, he can likely wed several more wives, give them all credit cards and still outlive his wealth. It requires a third generation (his grandchildren) to destroy a fortune.

His main concern should be where he is going to find competent health care regardless of cost. It is going to be increasingly difficult to find decent medical care, at least in the U.S., although he can travel elsewhere, and I am considering India myself. It is the things that money cannot buy that Gates will need most in his retirement. However, if I were him I would build my own hospital and hire the last internist on the planet (a vanishing breed indeed).

Richard Lehmann, editor, Forbes Income Securities Investor; columnist, Forbes magazine

• Here are six bits of advice on how Gates should spend his retirement years.
• Form a third political party and run for president under the banner "Reboot"
• Conserve energy by replacing air conditioners with "Windows"
• Start a virtual Olympics for videogamers. Call them the Vista Olympics.
• Create a world series of bridge and put the ante at $1 million.
• Become the PC guy in the Apple commercials.
• Take up a sport: Buy a team.