I can see why, on a theoretical basis, presidential term limits could provide some check (however ineffective) against dictatorship. After all, it seems likely that a third, fourth, or fifth term leader would be better able to convince the populace that he or she is more important than the position. Historically, though, presidential systems have almost invariably led to dictatorship regardless of the individual rules, so I doubt term limits alone does that much good. We would be much better off in the long-run with a parliamentary system, though even that is no guarantee.