No, I do not run one but I work in one. I am just curious. I hope you are not operating on a very razor-thin margin.
Most programmers are very opinionated. It is very easy to ask them about their opinion on how to improve the project, how to decrease cost, and so on. I'd suggest doing that as it costs pretty much nothing extra.
From reading Jeff Atwood, my opinion is that the person who goes above and beyond to make himself replaceable is the one you want to keep. I am not a manager though and I am sure there is a lot more to it than I know.
it is important mainly to identify which employees are not profitable, especially in fixed price projects.
do you run a devshop?