Ric I think we already have term limits, in that we can vote them out.
Long term senators, like Ted Stevens or Byrd in WV or Ted Kenedy, are good at doing what the Senate structure forces them to do–deliver pork and short circuit local initiatives for change. Massachusetts ia s big complicated state, with a lot of different and competing interests. No person can represent them all except in a very general way. Representatives, Congressmen, can represent the interests of a district, which are much smaller and much more focused. Senators instead represent all of Massachusetts or all of texas, which is really an abstraction. Since they can’t really work on local politics, they tend to focus on staying in power by delivering the pork, or by grandstanding in committees. Term limits wouldn’t change this tendency, I don’t think, because it’s written into the structure of the Senate.
As I understand it the origins of the Senate really lie in the slave state/free state controversy, and slave states not wanting to get outvoted by the more populous free states. In those days South Carolina could more reasonably be imagined as a state with a single interest–slavery–which was different from the interests of New York. But now South Carolina wants pretty much the same thing NY state does–economic growth, job creation, etc. The Senate is the legacy of a very different political order.