Disclosed is a method of using observed traffic pattern data to improve sleep mode efficiency in a radio handset. The radio handset determines quality of service (QoS) requirements of an application currently executing on the radio handset and selects a pre-defined sleep mode mask from among a plurality of pre-defined sleep mode masks wherein the selected pre-defined sleep mode mask provides the closest available match in terms of sleep/listen pattern to the QoS requirements. The traffic pattern data between the radio handset and a serving basestation is observed while under the initial sleep/listen pattern of the selected pre-defined sleep mode mask or the reactivated sleep/listen pattern after sleep mode deactivation. An alternate sleep mode mask is created based on the observed traffic pattern data between the radio handset and the serving base station wherein the alternate sleep/listen pattern is better suited to the actual traffic pattern than the initial sleep/listen pattern of the selected pre-defined sleep mode mask or the reactivated sleep/listen pattern after sleep mode deactivation.