Federal and postal workers who are piggybacking on their private-sector spouses' health insurance plans--to avoid paying premiums under the federal program--are playing with fire. They are risking major financial and medical hardships when they retire in order to save a few bucks on health premiums while they are working.

Each year, hundreds of federal workers find out--the hard way--that they cannot have federal health insurance coverage, ever, when they retire. Some don't find out until too late--after they retire--that they can't get coverage under the federal group rate health program. Despite their long careers, they never got the word--or paid any attention to warnings--about the five-year rule!

Any federal worker who doesn't belong to the Federal Employee Health Benefits Program needs to sign up next month when the insurance open enrollment begins. Workers can sign up for any of the plans in the federal health program. And if they remain in the FEHBP for the five years before retirement, they can take their health insurance coverage (and provide it for their spouse) into retirement.

At a time when many agencies plan to offer buyouts and/or early retirement, many federal workers may find themselves with the opportunity and an incentive to retire before they intended.

But if federal workers retire without being enrolled in one of the federal health plans for the five years before retirement, they probably won't be eligible for federal health insurance coverage in the years they will most need it.

Here's the deal:

When the private-sector spouse retires, his or her health benefits may be reduced or eliminated, or premiums could skyrocket. It is up to the spouse's employer. Also, the spouse of the private-sector employee may not be eligible for coverage when the private-sector spouse dies.

By contrast, federal workers--when they retire--can keep their health insurance coverage for life for themselves and their spouses. The retired federal worker (and his or her mate enrolled in a family plan) gets the same health plan choices, receives the same level of benefits and pays the same premiums in the same plans as younger, healthier civil servants.

Unfortunately, in a town like Washington with a high percentage of mixed marriages (one a fed, one not), some families run into health insurance problems just at the time--when they are older and less healthy--they most need good coverage.

To protect themselves--and family members--federal workers should be enrolled in one of the federal health plans (it doesn't matter which one) at least five years before retirement. That five years of coverage guarantees they--and their spouses--can keep health coverage, for life, as part of the federal group plan.

The other thing federal retirees must do--to ensure that a spouse keeps health coverage--is provide the spouse with a survivor benefit. It can be any amount, but there must be a benefit to make the spouse eligible to retain coverage under the federal health program.

Insurance experts recommend that federal workers join one of the low-cost federal health plans during the coming open season--and remain in it or another low-premium plan--to satisfy the five-year rule. That way when they retire they can be eligible for federal health insurance coverage (along with their spouses) at a time when their spouses' private-sector plans may become less desirable, more expensive or nonexistent.

Here's the official word on protecting coverage from the Office of Personnel Management:

"In order for you to continue your health benefits enrollment into retirement, you must: (1) have retired on an immediate annuity (that is, an annuity which begins to accrue no later than one month after the date of your final separation); and (2) have been continuously enrolled (or covered as a family member) in any Federal Employee Health Benefits Program plan (not necessarily the same plan) for the five years of service immediately preceding retirement, or if less than five years, for all services since your first opportunity to enroll."

Retirees must--as stated earlier--also provide some kind of survivor benefit to guarantee that their surviving spouses will be able to remain in the federal health program for life.

Bottom line: You can spend a few bucks now--paying premiums for a low-cost federal health plan even if you don't use it--or you can save that money by relying totally on your spouse's private-sector plan and, maybe, pay a lot more later.

Mike Causey's e-mail address is causeym@washpost.com