In a word: life.

The idea that Supreme Court Justices have life tenure is true for the most part, but there's a catch. Actually, if you look at the Constitution itself, the clause we now interpret as meaning "Justices have life tenure" only specifies they have "tenure during good behavior": From Article III of the US Constitution: "The judicial Power of the United States, shall be vested in one supreme Court, and in such inferior Courts as the Congress may from time to time ordain and establish. The Judges, both of the supreme and inferior Courts, shall hold their Offices during good Behavior..." The crucial distinction is that under our system of governement, Justices have life tenure, but can be impeached for misconduct. Theoretically, this ensures that no one is above the law and there is a check on the power of the courts. However, the judicial impeachment process can be abused by legislators who think the Justice in question "makes wrong decisions" and want to get rid of him. As was the case with the impeachment of Justice Samuel Chase, politicians occasionally misuse the judicial impeachment process to achieve purely political ends. The last time this country faced a politically-motivated impeachment investigation of a Supreme Court Justice was in 1972, when Gerald Ford launched a campaign to remove ultra-liberal Justice William O. Douglas from the Court. The rules of the game were forever changed, as this quote from Ford shows: "What, then, is an impeachable offense? The only honest answer is that an impeachable offense is whatever a majority of the House of Representatives considers it to be at a given moment in history; conviction results from whatever offense or offenses two-thirds of the other body considers to be sufficiently serious to require removal of the accused from office." That said, the Machiavellian answer to "How long is one term of a US Supreme Court judge?" is "however long two-thirds of the Senate wants it to be".

They are appointed for life.

Lifetime appointment

As long as the judge lives, or is incapacitated or retires.

It is a lifelong appointment

Why is it so long ? Is it so they can cover up corruption? Some of those old fools should be retird years ago they are stealing your childrens future just like Joe Biden . Its time a lot of old fools were held accountable for their actions.