The growing need of responsiveness for manufacturing companies facing market volatility raises a strong demand for flexibility in their organization. Since the company personnel are increasingly seen as the core of the organizational structure, a strong and forward-looking management of human resources and skills is crucial to performance in many industries. These organizations must develop strategies for the short, medium and long terms, in order to preserve and develop skills. In this work, we look at the lineup of multi-period project, considering the problem of staff allocation with two degrees of flexibility. The first results from the annualization of working time, and relies on policies of changing schedules, individual as well as collective. The second degree of flexibility is the versatility of the operators, which induces a dynamic view of their skills and the need to predict changes in individual performance as a result of successive assignments. We are firmly in a context where the expected duration of activities is no longer deterministic, but results from the performance of the operators selected for execution. We present a mathematical modeling of these skills, and an example of scheduling problem, which resolution is based on genetic algorithms.