If the company has fewer than 20 employees, then the law does not require the company to continue group insurance for its retirees. However, many small companies offer to continue insurance benefits voluntarily. If you experience any of the events listed above, you can choose to continue your group health insurance, but the time allowed will vary. For example, on retirement you can continue your group health insurance up to 36 months. If you are fired or are switched to part-time employment, you may elect to keep the group insurance for a period no longer than 18 months.
Some companies voluntarily offer longer periods.
If you decide to continue your health insurance, you have to inform the plan administrator within 30 days of the trigger event. You will be legally required to continue to pay premiums for your insurance. If the company stops offering insurance to its employees in general, then the law allows your coverage to be terminated. The company can also stop your coverage early if you fail to pay the required premium or if you purchase other group health insurance. These laws are complex, and I have only given you an overview here.