There are a number of factors that may need to be taken into consideration when you retire, one of them being whether or not your spouse is going to retire at the same time as you. So before making any decisions, make sure you ask yourself these important questions: "What will my spouse be doing after retirement?" "How old is my spouse compared to me?" and "What will our finances look like after retirement?"
Your spouse may retire at the same time as you, they may retire before or after you. Regardless of when your spouse retires, if their employer does not offer group insurance policy (or any group insurance policy) then you will require two separate policies; one for yourself and another for your spouse. If your spouse's employer does provide a group insurance policy then one policy will cover the both of you.
If your spouse plans on continuing to work after retirement, they need to purchase their own separate policy when you retire. If your spouse decides not to work after you retire, they may be able to join your group insurance plan by following the rules that govern the coverage under that plan.