No more term limits

T.R. Fehrenbach, the conservative historian who writes a weekly column for the Express-News, is proposing limiting U.S. presidents to single terms.
He makes an interesting case based on history, however I am still completely opposed to the idea. I don't think it is true that every president's second term has been disasterous.
It is true that Lincoln may have had a tough time politically during a second term had he not been assassinated, but I think there can be little doubt that he would have still been much better than Andrew Johnson or Ulysseus Grant or any of the other corrupt, post-war presidents we ended up with.
FDR's second term was certainly not a disaster, as Fehrenbach implies, and his subsequent term was successful as well due to his leadership during WWII.
Eisenhower's second term wasn't much different from his first one. Kennedy had the potential to do very well had he had a chance at a second term.
Nixon, of course, was impeached during his second term, but the things that set Watergate into motion happened during his first term.
Reagan clearly had troubles during his second term with Iran-Contra, but it wasn't enough to sour his political support and he probably could have won a third term easily, but instead passed it on to George H.W. Bush.
Bill Clinton's second term was a huge success other than the distraction of the Monica Lewinsky scandal. But as far as things that actually impacted people's lives, he had great successes during his second term.
And George W. Bush obviously was awful during his second term, but I would argue that he was awful during his first term as well but managed to cover up his failures and incompetence in the aftermath of 9/11. Osama Bin Laden was responsible for Bush's second term more so than Karl Rove.
Now that we have Obama in there, Fehrenbach is suddenly raising the spectre of limiting presients to one term. Why wasn't he making that argument four years ago?