The constitution would need to be amended to change this, as it was for presidents when Republicans were petulant about FDR's 4 terms, as if that were bad for the nation.
On the larger topic, I'm very much against term limits. I think our nation benefits from good representatives serving fo decades, and we'd shoot ourselves in the foot to ban it.
But what about the hacks who hold seats simply because of incumbency advantages, the parties having too much power - isn't that reducing democracy?
I'd say yes, but that the benefits are high enough that we should limit our reforms short of term limits, and find better ways to fix the problem of incumbency advantages.
I don't suppose all of our libertarian friends would accept any role for citizens to take some personal responsibility not to vote for bad incumbents - but of course, there's more to the issue, and I think most of it has to do with the role of money in buying name recognition, and we should change the role of money, which is largely an alternate way for the powers to maintain their disprortionate influence and get around the intent of democracy.
In my view, term limits brinigng about a legislature filled with fresh faces only serves the experienced unelected bureacracy who gain the upper hand in how the system works, and the party interests for whom the actual performance of the person is less of an issue in the election than the marketing of yet another new face constantly, 'trust us! new and improved!' You know what you are getting with Ted Kennedy and Trent Lott.
There's something to be said for that.
They aren't picked by some machine recently, who they owe more to for that selection than the constituents, lame ducks without the accountability of re-election.