I believe that allowing congresspeople to stay in congress promotes unhealthy relationships between members of congress and the lobbyists that are destroying this country. Too many of our representatives are worried about keeping the lobbyists happy, and not recognizing the needs of the American People.
Term limits are in effect in various forms of our government, to great success. Power corrupts, it is in our nature as humans - it is unethical to allow our lawmakers to retain their seats for extended periods of time.