I seem to be saying that a lot.

Are we talking about a punishment that will stop OTHER people from commiting crimes?
If so, then I agree with Andrew. Nothing will stop people who don't plan beyond tomorrow. And most of the criminals out there are that type. Otherewise they wouldn't make such stupid mistakes and get caught.

If we're talking about stopping the person who committed the crime from doing it again, then death is no different from life inprisonment.

Which seems to be where the 3 strike rule is helping. Repeat offenders are locked up forever. At least, in Seattle the crime rate is dropping.

Given a set population
with X criminals (repeat)
Then locking up Y criminals means that only X-Y criminals are available to committ said crimes.

Well, in theory. In practice, the varieties of the human population shift the results back and forth.

To be truly effective, this would have to be combined with social programs aimed at preventing kids from becoming new criminals.