(MONEY Magazine) – Come 100 insurance companies now offer coverage for long-term care in a nursing home (or, in some cases, the patient's own house). Although it may seem like essential protection against admittedly crushing costs, these high- priced policies are rarely worth the premiums, which typically range from $350 to $3,000 for people age 65 or more. For one thing, the odds of having to pay for long years of nursing-home care -- the greatest expense threatening the elderly -- are far lower than the misleading numbers often quoted by insurers. It's true that an average of one out of every four Americans age 65 or older spends some time in a nursing home. But the probabilities look vastly different if you take other circumstances into account. Because women have a longer life expectancy, the probability that those 65 or older will spend time in a nursing home is one in three, compared with a one in five chance for men of the same age, according to a study by Erdman Palmore, a gerontologist at Duke University in Durham, N.C. Stays of more than a year -- the kind that are almost never covered by Medicare -- are far rarer for both sexes. Elderly women have an 8% chance of living in a nursing home that long, men less than 5%. People who are very self-reliant or who receive help from relatives or their communities tend to remain independent in greater numbers than even these averages. If your parents' histories do suggest that they are prime candidates for a nursing home, you should note that even the most comprehensive long-term-care policies will pay only a portion of the costs of their care. For example, the plans typically pay a fixed daily amount of $50 to $80, which will almost certainly not cover costs after several years of intervening inflation. Waiting periods of 20 to 90 days before benefits begin are also common. As a result, your parents may be far better off putting aside each year a sum equal to the premiums on an average policy and investing the money to build their own emergency fund. For instance, if your parents each invest $1,500 annually starting at age 70 -- about what they would owe on a typical policy -- they will have an amount equal to nearly a year's nursing-home coverage, after deductibles, by the time they turn 80. If you don't trust your parents' ability to save or if you worry that they may be early candidates for years of custodial care, then you may be wise to take out a long-term-care policy. Look for the best coverage at the cheapest price -- premiums are no reflection of comprehensiveness. The better plans pay benefits for home care as well as for common brain disorders like Alzheimer's and do not restrict your parents' rights to renew. For more detailed guidance on how to shop for a policy, send for The Consumer's Guide to Long-Term Care Insurance, free from the Health Insurance Association of America, 1025 Connecticut Ave. N.W., Washington, D.C. 20036.