This is one place you may have an advantage over married couples. The cost of commuting, buying work clothes, and eating out for lunch may go away, but your health expenses will probably increase with age. Add to this, the fact that a bag of groceries twenty years from now will probably cost a lot more than it does today. Partly true partly false. If your partner dies before his or her retirement, you may be out of luck.
Some plans have no provision for passing proceeds to anyone other than a married spouse.
Retirement plans that are funded entirely by the employer typically fall into this category. Life insurance can help solve this problem before and after retirement. Only legally married spouses are protected. I will collect my disability insurance as long as I live. Practically all individual and group disability benefits end at age 65.