I have always thought that term limits for Justices sound good until you really give the issue some thought.
Many studies or theories by political scientists fit some subset of cases that a court decides, but literally no theory can account for all of them, particularly when it comes to studying a complex institution like the Supreme Court.
I find it hard to believe that Senators or the American public will classify Sotomayor as unqualified, particularly given the thin credentials of many of our eighteenth and nineteenth century Supreme Court Justices.
Empirical evidence collected and analyzed by political scientists demonstrates that judicial pensions are the most important factor in a Justice's decision to retire, far more important than the party of the President or which political party has control of the Senate.
I remain mindful that the role of a judge is a limited one and that judges can't solve every problem. But at the same time, judges play a crucial role in safeguarding liberty and protecting the rights of all citizens.