A method is provided for activation of Idle-mode Signaling Reduction (ISR) for a given mobile terminal based on behavior of the given mobile terminal, in a manner to minimize signaling load between the mobile terminals and the wireless network. The methodology operates to dynamically enable or disable ISR on a per-terminal basis, using the session arrival rate and timeout data for the mobile terminal. Based on these mobile-terminal behavioral criteria, and preferably using an iterative process at long time scales, the methodology operates to optimize the decision thresholds used to turn ISR on or off.