[dpritchett]

Why not negotiate a way to make the employee want to stay for the duration of the project? If the monthly salary isn't enough to ensure the duration of service you need, find a way to offer additional compensation.

Try back-loading the employee's contract with increasingly large incentives in the latter stages of the project. Any steps you take that limit the employee's career mobility and agency without employee agreement and compensation are suspect.

[shiven]

I do like this idea of a 'vesting'-like timeline. Especially in high-risk, high-turnover projects, tying final bonuses upfront to sticking till the project ends sounds like a rational solution.