The incumbent-protection racket that Congress has become is clearly not going to allow term limits to become the law of the land. At the Constitutional Convention in 1787, Alexander Hamilton proposed that U.S. senators be given life terms. Hamilton's critics accused him of being a monarchist. Hamilton's plan only covered the Senate. But it would be a start.
Life terms can indeed institutionalize incompetence, but so does the current system.
If you are worried about having David Bonior around for life, get over it, because under the system now, that's what you are going to have anyway. Even in 1994, with the Republican takeover of Congress and revolution in the air, 90.2 percent of incumbents were returned to power. I know that I am indulging in unconstitutional daydreaming, but better that than the current nightmare of deceit resulting from a Congress filled not with Scott Klugs or Steve Largents, who know the difference between what's right and what's expedient, but with men and women driven by the fear of what might become of them without an office on the Hill.