How long do Supreme Court justices serve?

What does this answer mean?

Supreme Court justices serve for life. USCIS accepts three ways to say it: for life, lifetime appointment, or until retirement.

Article III of the Constitution says federal judges, including Supreme Court justices, hold their offices "during good behavior." There is no term limit and no age limit, so a justice can stay on the Court until they choose to retire or until they die. A justice can be removed only through impeachment by the House and conviction by the Senate.

The Constitution also says judges' pay can't be reduced while they're in office. Together, lifetime service and protected pay are meant to let judges decide cases without worrying about losing their jobs or income, which is the answer to the next question on the test.

Compare this with the elected branches: members of the House serve two years, the president four, and senators six.

At the interview, say "for life."