Almost all the justices earned thousands of dollars teaching law school courses or judging moot court contests in the United States or abroad in 2008, and a few collected hefty royalties from published books or memoirs.
Many also took all-expenses-paid trips around the world to give speeches, with Justices Stephen Breyer, Anthony Kennedy and Antonin Scalia making dozens of appearances in 2008 alone. While the justices aren't allowed to be paid directly for their speeches under court rules, "they're not flying coach and they're not paying a cent for their travel or accommodations," Powe said.
Back at home, many justices do find ways to live like average Americans, residing in suburban Washington, D.C., homes and partaking in the area's social scene.
Expert say the lack of cameras in the courtroom has helped the justices retain some anonymity in public. A recent C-SPAN poll found many Americans don't know how many justices sit on the bench and most can't identify any by name.
"[Former chief justice, the late William Rhenquist] would often put on a hat and a trench coat and just go strolling around the building," McAllister said. "Tourists would be taking pictures and he'd walk right by."
After hours, the justices occasionally partake in public cultural and athletic events.
Scalia and Justice Ruth Bader Ginsburg frequent the opera, Justice Sonia Sotomayor remains an active salsa dancer and Justice John Paul Stevens has long been an avid golfer. During his free time, Thomas has traveled the country in his motor coach, spending nights on the road at campgrounds and national parks.
Kennedy, known to be one of the most social justices, is a regular on the Washington, D.C., embassy party scene. "He's an A-lister," Powe said.
Yet not everyone is convinced that living out one's days as a member of the high court is worth it – no matter the court's ability to shape U.S. legal thought and exert influence on paramount constitutional conflicts of the day.
"We're kind of doers," former President Bill Clinton said in a recent interview, dismissing the prospect of a Clinton on the high Court. "[Hillary and I] like being out there and doing things, rowing our own boat and making changes we could see happen."
Kansas' McAllister agreed. "People often tell me, 'You ought to go into the federal judiciary,'" he said. "I'm not sure I'd want to, having watched it."