Being 55 years of age, or a bit older, is still a good age to get affordable rates on term life insurance - being it a 10 or 20 year term.
If you are over fifty five you may not be able to buy a cheap 30 year term policy, but a ten or twenty year is very possible, and still affordable.
Getting good rates on a life insurance policy at your age will depend on your present health, if you had had any serious health issues (e.g. cancer, heart attack), if you smoke or use tobacco products, and if you engage in any risky behaviors.
There are many reasons why a person over the age of fifty five (man or woman) needs life insurance. Maybe they need to make sure their children's college education gets paid if they die; make sure their spouse is left with money to pay the mortgage on the family home; pay for their debts; and if the spouse does have an income, make sure the family keeps the same level of living they are accustomed to.
How much you will need in coverage will depend on the reasons mentioned above. You'll have to figure it out yourself. Only you know your personal details. You can use a handy life insurance calculator like this one.
Usually, it's recommended that you get a policy death benefit 5 to 10 times your yearly household income. But, this is not always feasible and can cost a lot. So, decide on an amount that you and your spouse fills comfortable with. It's better to be over-insured versus under-insured.