They could institute something similar for Supreme Court justices--they wouldn't be able to vote after their 80th birthday. It could be called the Montini Rule (if it was called the Paul VI Rule some people would be confused, thinking it had something to do with the Virgin Islands). Justices wouldn't be required to retire, but they would if they couldn't vote.
Something along the lines of taking “senior status.” I still would like to call it the “Rehnquist Amendment.” That’s all you’d need is to compare it a Catholic procedure (no matter how correct it is) and have all the leftists howling about church & state nonsense — of course, they’d oppose the amendment because of Stevens (but if the bench were full of near-90 year old Conservatives, you know they’d be jumping on the bandwagon).
Heck, might be a good idea for Congress, too. Of course, Ted Kennedy won’t hit 80 until February 2012. His liver, however, hit that about 40 years ago.