18 Years Worth of Days The average retirement lasts for 18 years. Are you prepared to fill that many days? Share | Have A Question About This Topic? Address Thank you! Oops! Related Contents Tuning Your Social Security Benefit When should you take your Social Security benefit? How Will Working Affect Social Security Benefits? Knowing the rules may help you decide when to start benefits. Retirement Plan Distributions There are a number of ways to withdraw money from a qualified retirement plan.