Ann Althouse highlights Rick Perry's judicial term limits proposal from this longer piece. (Note that Perry, in proposing to "overhaul Washington DC" is not talking like a conservative, but I will leave that discussion for another time.)
Too many federal judges rule with impunity from the bench, and those who legislate from the bench should not be entitled to lifetime abuse of their judicial authority.” He proposed 18-year terms, staggered every two years, for new Supreme Court justices, and suggested similar limits on federal appellate and district court judges...
I like judicial term limits in principle, but the practical effects wouldn't be apparent for decades. The average Supreme Court term is 16.71 years. In the modern era (since Earl Warren, and excluding the incumbent justices) that average has trended up to 20.32, so there might be some slight advantage, but not much.
Another problem is that the effects presumably would have to be phased in. Even if we assume that Perry gets his amendment in early 2013, it is not reasonable to suppose that he would get a judge through the nominating/confiramtion process before 2014 -- a mid-term election year. Each term limit after that would also fall on an election year which would put quite a bit of political pressure on the Senate.
Also, note the unfortunate order in which the current justices would rotate off:
Scalia 2014 (Mid-term)
Kennedy 2016 (Presidential)
Thomas 2018 (Mid-term)
Ginsburg 2020 Presidential)
So Perry's crusade against judicial activism would have the following results:
1. In the two easiest nominations, he would be forced to replace the two strongest conservatives. Hopefully he could find suitable candidates, but the benefits to the overall state of the court would be at best neutral.
2. His battle to replace moderate Kennedy with a conservative would certainly be a factor in his re-election bid in 2016. Lot of down-side there for very little improvement.
3. He would have to wait until the last year of his second term (assuming he survives the 2016 election) to replace his first liberal. That nomination fight would occur in his lame-duck year and would substantially impact his successor's chances.
4. That successor would be replacing Steven Breyer, which would certainly be a factor in the election.
On the whole, I don't see much upside in the political dimension and a lot of downside. Maybe the principle is worth the risk. I do like the fact that we would know when justices are up for replacement, and could decide whom to vote for accordingly. But that benefit would be more of a side-effect and isn't really the point of Perry's proposal.