U.S. Supreme Court Justices are appointed by the President and usually have their posts for life if they so choose. While most have served an average of 16 years, others (such as Associate Justice William O. Douglas) have served as many as 36 years, and the term lengths have increased over time in general. So why the lack of limits?

The lack of term limits is supposed to ensure that justices won’t be swayed by politics or popular opinion while they make some of the most important decisions in American law. It also wouldn’t be fair for one president to choose many justices only because their terms had all expired, though term limits could be staggered to avoid this.

Another reason for the lack of limits stems from the fact that people tend to live longer than they did in the 1700s, when the Supreme Court was established. When the average lifespan was only 39, the founders of the Court simply weren’t considering the possibility that justices would serve 20 or even 30-year terms.