Before nominating 53-year-old Brett Kavanaugh to the Supreme Court, President Trump expressed a hope that his pick would serve for 40 to 45 years. That was wishful thinking: The longest-serving justice in history, William O. Douglas, lasted over 36 years but was so obviously incompetent toward the end that his colleagues conspired to decide no closely contested cases until he stepped down.

Still, Kavanaugh is likely to serve a long time by our standards, and a very long time by the standards prevailing when the Constitution was framed. For most of American history, justices left the court at an average age of below 70. Today it’s about 80. They used to serve about 15 years, but now average more than 28 years. (For scale, consider that 28 years ago, about 38 percent of the U.S. population had not yet been born.) As much as justices appear to enjoy these extended careers, their unlimited terms are dysfunctional for the judicial system, the court itself, the presidency and Congress. We need term limits for the court.

Right now, justices race against senility, physical decrepitude and death itself in order to hand the power to appoint their successor to a specific party. Justice Anthony M. Kennedy was appointed by a Republican, and to few people’s genuine surprise, retired with a Republican in the White House. That’s how it usually works. In a 2010 article, we calculated that the odds of a justice retiring rise 168 percent during the first two years of the term of a president of the same party. Justices also tend to avoid retirement when the sitting president is not of the same party – a delay that triples their odds of dying in office.

These distorting effects add up. While it might seem that things would average out over time, that doesn’t happen. From Dwight D. Eisenhower’s presidency through Barack Obama’s, six presidents were Republicans and five were Democrats, but that didn’t lead to similar numbers of appointments for each party. Rather, Democrats appointed eight justices, while Republicans appointed 17. Much of the imbalance comes from Eisenhower and Richard M. Nixon, who appointed nine justices between them – more than the five Democratic presidents combined, in spite of Nixon’s premature departure from office.

Long tenures on the court also provoke a fear, reasonable or not, that an ill-considered appointment could damage the nation for a long time. That fear worsens already acrimonious confirmation hearings, often marked more by exaggerated claims and character assassinations than with evidence of the quality of jurisprudence that a nominee would bring to the court.

Term limits of 18 or 24 years for Supreme Court justices would fix many of these problems. Under staggered 18-year term limits, for example, one of the nine seats could be filled every odd year. If any justice died or retired before the term was up, a replacement would fill only the remainder of that term. Thus, there would be no partisan advantage in retiring early because doing so would not change the schedule of regular appointments.

After completing an 18-year term, justices could still serve on lower courts, thus technically preserving their life tenure as a federal judge, though not all of it would be on the Supreme Court. Such a fundamental change in the meaning of life tenure would probably require a constitutional amendment, although not everyone thinks so.

Adding court term limits to the Constitution stands a better chance than some might think. A constitutional amendment requires ratification by three-quarters of the states, and judicial term limits are well established in the states. Term limits or maximum judicial ages are used by 49 of 50 state supreme courts (the only exception is Rhode Island), as well as the high courts of other highly developed countries.

If there is an impediment, it’s Congress. Senators and representatives might, in the abstract, favor term limits for justices, but might not want to encourage anyone to start thinking about term limits for the legislative branch.