The longevity of each MPC application is strongly related to its performance maintenance. This work provides an overview of the methodologies available to fulfill this task, including a discussion about some special requirements of performance assessment methodologies for typical industrial MPC applications. The available methodologies were compared using these requirements. The best approaches were selected and compared to a new method proposed by the authors. These techniques have been applied in two case studies: the Shell benchmark process and the quadruple-tank process. The results show that the control policy (setpoint, soft constraints, targets) followed in the MPC application should be the determining factor in selecting the methodology for performance assessment.