Strange math and strange predictions

George Mason University School of Law professor Ilya Somin has a post about how little coverage is being paid to the possibility that President Obama or Mitt Romney will get to pick a Supreme Court justice during the next four years.  Professor Somin writes

. . . this election could have a huge impact on the future of the Court. Even if a reelected Obama gets to relace two liberal justices with younger liberals or Romney gets to replace two conservatives with younger conservatives, that will still have a profound impact. There’s a big difference between a justice who is likely to be around for only a few more years, and one who could well serve for thirty years or more. Given increasing life expectancies, a justice who is in his or her early fifties when appointed could easily serve until 2050 or even later.

Note the could in the first sentence.  It might or might not have "a huge impact on the Court."  Perhaps that unknown is why few are discussing it.  However,  let's assume that the two appointments occur and that they do so in 2014 before both parties are gearing up for the 2016 presidential election.  Professor Somin assumes that these new justices might serve beyond the year 2050.  A fifty-year-old appointee in 2014 would have to serve until they are 88 in order to still be on the court in 2050.  Since professor Somin is assuming that Supreme Court justices serve until they are 88, which Supreme Court justices will be 88 during the next presidential term?

The answer is none of them.  In 2016, Justice Ginsberg will be 83. Justices Scalia and Kennedy will be 80.  Justice Breyer will be 78.  The remaining justices will all be under 70.  It seems to me that Professor Somin's math does not add up.  If one is going to assume a new justice will sit until they are in their late 80s (or 90s given that the professor talks about an appointee "in his or her early 50s), then it seems like one should also assume that the current justices will

Moreover, as we have discussed before, supreme court justices do not resign because a president with whom they are ideologicially sympathecic is in office.  They resign either because they died or because their health (or in Justice O'Connor's case the health of a loved one) won't let them do the job anymore.  I doubt that two liberal justices will retire if President Obama wins re-election.  I also doubt that any conservative justice will step down if Governor Romney wins the election.

Finally, if you look at this list of Supreme Court justices by tenure, you will see that only 13 of the 112 people appointed to the Supreme Court have served more than 30 years.  Only 5 have served the 34+ years that Professor Somin contemplates with his hypothetical appointees (although William Brennan and the first John Harlan came very close to 34 years).