Social Security: By the Numbers Here are five facts about Social Security that might surprise you. Share | Related Content 18 Years’ Worth of Days The average retirement lasts for 18 years, with many lasting even longer. Will you fill your post-retirement days with purpose? When Should You Take Social Security Monthly Social Security payments differ substantially depending on when you start receiving benefits. A Look at Systematic Withdrawals This calculator may help you estimate how long funds may last given regular withdrawals.