Generally, to continue FEHB coverage as a retiree, you must retire on an immediate annuity and you must have been continuously enrolled under the FEHB program (or covered as a family member) for the five years of service immediately preceding your retirement or, if less than five years, for all service since your first opportunity to enroll. This five-year requirement will be waived automatically in certain situations, mainly involving early retirement and involuntary separation due to downsizing; waivers can be granted for certain other reasons but those are rare.
Employees who separate and are eligible for a deferred annuity cannot begin health insurance coverage when their deferred annuity begins.
If you keep FEHB as a retiree, you can continue to cover eligible family members. Plan premiums are the same as for active employees (note: postal retirees pay more than active postal employees because an additional employer-paid share for postal employees does not apply to retirees) although premiums effectively are more expensive because retirees cannot pay them on a pretax basis.