Federal judges in the United States serve for life, or until they choose to retire, as long as they maintain "good behavior." This provision is established in Article III of the U.S. Constitution.
The Founding Fathers intended for federal judges to serve life terms to ensure judicial independence. By removing the threat of constant reappointment or election, they aimed to insulate judges from political pressures, allowing them to make decisions based on the law and the Constitution rather than on popular opinion or political considerations. This independence was seen as essential for maintaining the rule of law and protecting minority rights against potential tyranny of the majority. The idea was to create a stable and experienced judiciary that could withstand the whims of political change.