It's not enough just to save for retirement. You also need to make sure your money lasts once you quit working.

How long you stretch those dollars depends on variables such as your age at retirement, your health and inflation. A healthy lifestyle and savvy career maneuvering can help you manage the first two challenges. But many people don't pay enough attention to inflation, says Steven Kaye, CFP and president of American Economic Planning Group.

"Most people have some understanding of the basic definition of inflation. They may know a loaf of bread will cost $10 one day," says Kaye. "But because inflation comes in very tiny doses -- just 2 percent to 3 percent a year -- most people don't fully appreciate its impact."

Loaf of bread once cost a nickel
Historically, inflation has clipped along at an annual 3-percent pace, on average. That means if you currently live on $50,000 a year, in 30 years, you'd need around $121,000 annually.  

What do you do about price hikes? Plan conservatively, says Dee Lee, author of "Let's Talk Money." She advises clients to assume inflation will grow higher than traditional averages -- at least 4 percent annually.

"In retirement, the very goods and services we need as we age increase much faster than the normal inflation rate," Lee explains. "Health care, for example. The flat-screen TV and the new computer have come down in price, but the costs of medication and tests have increased."