Term limits encourage regular, competitive elections; they improve citizen access to the process; they bring a broader range of experience and perspectives to the legislature; they improve the incentives faced by sitting legislators and they widen the circle of those with intimate knowledge of state government. In sum, term limits bring the legislature closer to the people.
If there are term limits, then members of Congress might finally start acting in the interest of their constituents instead of the interest of lobbyists and other special interests they currently rely on for reelection.