Prior to FDR, no president had ever served more than two terms because it's a goddamn impossible job that pretty much drains the life out of anyone who does it for eight years. Having said that, there's no reason, none, to limit the number of terms a president can serve.
Or, we can look at any number of parliamentary systems like Canada, Australia, the U.K., Italy, Spain... no limits of the number of terms that can be served, but that doesn't translate to Prime Ministers for Life, since eventually either the population gets tired and throws out the government, or the ambitious members within the party force the man at the top out. Political turnover is healthy, but in an already healthy democracy, turnover for its own sake makes little sense.
Like I said, reality kept every president prior to the 22nd to two terms, and if another situation comes by where we have/need an FDR to serve four terms, I don't want that stupid-ass amendment to stop it from happening.
I'm thinking of a number between 1999 and 2001...
Fictitiously yours, Trent Roman