I'd rather not have a limit for anyone. Not everyone is suited to be a statesmen, and some are better than others. I think if you are getting reelected you are obviously giving the people something more, perceptibly, than the other candidates will. As Spik already pointed out, if we all agreed to run Constitutionally, term limits for president wouldn't be much of an issue.
We should focus on following the constitution before we decide if term limits are actually necessary or not.
I think even if we aren't following the Constitution, term limits do little to help lead us in that direction. If the people want FDR, they are going to get FDR-style leaders even if it isn't FDR himself. I doubt FDR would have been president for an extremely long time, especially if he kept expanding the Federal governments powers. Small-government people are strong in this country.
How long have you worked at one job before? People get too comfortable in the same position for too long. They get lazy, they get sloppy, they learn how to manipulate their position, etc. IMO we need more term limits; career politicians should not exist.