Stability of the Cost Performance Index (CPI) and Schedule Performance Index (SPI(t)) refers to the moment in the project life cycle at which the CPI and SPI(t) are accurate and constant. For a project manager a reliable CPI and SPI(t) is essential for taking corrective actions in time to keep the project on budget, planning and scope. The focus of this paper lies on identifying project characteristics which influence this moment of CPI and SPI(t) in the project life cycle. Both existing theories from earlier academic research and newly identified project characteristics are tested by using empirical data from nine projects executed by an engineering and consultancy company in the Netherlands. It is found that some project characteristics influence the moment of CPI and SPI(t) in the project lifecycle whereas other do not. The results of this paper contribute to the body of knowledge on EVM and might provide valuable information to project managers who consider to use EVM in their projects. The results of this research also point out new areas to explore the understanding of the stability of CPI and SPI(t).