I have about $700,000 and plan on retiring soon at age 62. How can I make this money last at least 30 years? -- Steve, Vevay, Ind.

Making sure your money lasts isn't your only goal for retirement. Presumably, you also want to be able to draw enough from your savings to live relatively comfortably the rest of your life. And I assume you would like to have some flexibility about how you tap this nest egg, so you can fund not just regular living costs but unexpected expenses and the occasional splurge.

I mention this not to quibble, but because understanding that you actually have several goals is important when deciding how to manage your $700,000 stash.

If making sure you didn't outlive your nest egg were your only consideration, you could simply put your entire 700 grand into an immediate annuity, a type of investment that gives you a monthly check the rest of your life. As long as you're prudent about how you go about it -- sticking to highly-rated insurers, spreading your money among enough companies to assure you're fully covered by your state's insurance guaranty association -- you could sit back and collect $3,600 a month, possibly more, for as long as you live.

But you would also give up something -- namely, access to your money. Once you buy the annuity, you can no longer dip into your stash for emergencies and such. You receive only the monthly payments. And unless you buy an immediate annuity with an inflation rider -- which usually means accepting an initial payment that's about 25% less than one without inflation protection -- the purchasing power of your monthly check will decline throughout retirement.

Such shortcomings are why putting your entire stash in an immediate annuity probably isn't the right way to go.

There's another option, however, that can give you the flexibility you need, plus a good shot at inflation protection. Just invest your 700 grand in a relatively conservative mix of stock and bond funds -- say, 50% stocks-50% bonds -- and withdraw the cash you need each year.

To increase the odds that your money will last at least 30 years, you could follow what's commonly referred to as the "4% rule" -- that is, withdraw 4% of your nest egg's value the first year of retirement, $28,000 in your case, and increase that amount by the inflation rate each year to maintain your purchasing power.

Although the probability can vary depending on the assumptions you make about inflation and investment returns, there's roughly an 80% chance your money will last at least 30 years if you follow this regimen. Plus, you would have the opportunity to dip into your stash for extra cash should you need it.

But this approach has drawbacks, too. One is that while your chances of running out of money too soon are low, they're not zero. There is still a meaningful risk. That's especially true if your investments take a big hit early in retirement. In that case, the combination of investment losses, plus withdrawals could so deplete your portfolio's value that your nest egg could run dry well before 30 years.

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How to Make Your Retirement Savings Last