Term limits have everything to do with the revolving door representation has become; indeed, it pre-selects candidates because their sponsors much come up with sufficient cash to get a nameless stooge elected in the first place. Because our representatives are looking at a definite termination date, they must set up an exit strategy. That means they have to start selling out earlier than they otherwise might if the option of keeping their jobs was still open.
Madison argued most of this rather ably in Federalist 53.