As a personal preference, I've never been a fan of forced term limits because I believe the people voting should make decisions based upon performance rather than favors received, though I know many people don't pay enough attention to be able to do such.
I have supported individuals who self-limit their terms and believe that is a good way to address the issue without passing laws that would harm good legislators. But this quote below details the existing system and how it has been corrupted by career politicians and makes a good argument for term limits.
"Legislators like pork because it helps them get reelected. They are interested in administrative details because long tenure promotes narrow specialization. The constituent service racket allows lawmakers to ignore big problems by fixing small ones. In becoming ombudsman -- glorified errand boys, -- incumbents build up enough good will for most to survive even a watershed year like 1992. By ending Congressional careerism, term limits will encourage attention to larger legislative issues. By changing the understanding of the legislator's role, term limits are probably the most effective single reform that can be imposed on Congress. And imposed it will have to be: While great majorities of the American people support term limits, lawmakers oppose them in even larger proportions. With a career Congress, voters face a dilemma: They do not like paying taxes to Washington and hoping to get them back in the form of pork and entitlements, but as long as the system is rigged, it makes sense to vote for the incumbent to maximize your own take. Congressmen face a similar dilemma: Take the easy road to reelection or face the often difficult choices of balancing local and national interests. Take away the career mindset and both representatives and voters can make choices based on the merits of each case. ... In fact, one of the biggest benefits of non-professional legislators is that they would be unlikely to join with the bureaucrats and special interests in blowing smoke at the voters." ~ Eric Felton