A portable apparatus comprising: at least one memory for maintaining configuration information comprising at least information on a target operational time of the portable apparatus and information on one or more periodic actions scheduled to be performed periodically by the portable apparatus; means for performing the one or more periodic actions according to the configuration information; means for measuring power consumption due to each of the one or more periodic actions; means for determining an estimated remaining operational time for a current charge of a battery powering the portable apparatus based on the measured power consumption; means for reducing the target operational time according to passing of time; means for comparing the estimated remaining operational time to the target operational time; means for lengthening one or more periods of one or more respective periodic actions defined in the configuration information to reduce battery consumption, in response to the estimated remaining operational time being shorter than the target operational time; wherein the portable apparatus is configured for maintaining, in the memory of the portable apparatus, information on a plurality of power consumption values, each power consumption value of the plurality of power consumption values corresponding to a different operational time, and wherein the estimated remaining operational time for the current charge of the battery is determined by at least performing, by the portable apparatus, the following: compare averaged measured power consumption value to the plurality of power consumption values maintained in the memory; and select an operational time corresponding to a power consumption value of the plurality of power consumption values maintained in the memory and closest to the averaged measured power consumption value or to the smallest power consumption value of the plurality of power consumption values maintained in the memory that is larger than the averaged measured power consumption value. at least one memory for maintaining configuration information comprising at least information on a target operational time of the portable apparatus and information on one or more periodic actions scheduled to be performed periodically by the portable apparatus; means for performing the one or more periodic actions according to the configuration information; means for measuring power consumption due to each of the one or more periodic actions; means for determining an estimated remaining operational time for a current charge of a battery powering the portable apparatus based on the measured power consumption; means for reducing the target operational time according to passing of time; means for comparing the estimated remaining operational time to the target operational time; means for lengthening one or more periods of one or more respective periodic actions defined in the configuration information to reduce battery consumption, in response to the estimated remaining operational time being shorter than the target operational time; wherein the portable apparatus is configured for maintaining, in the memory of the portable apparatus, information on a plurality of power consumption values, each power consumption value of the plurality of power consumption values corresponding to a different operational time, and wherein the estimated remaining operational time for the current charge of the battery is determined by at least performing, by the portable apparatus, the following: compare averaged measured power consumption value to the plurality of power consumption values maintained in the memory; and select an operational time corresponding to a power consumption value of the plurality of power consumption values maintained in the memory and closest to the averaged measured power consumption value or to the smallest power consumption value of the plurality of power consumption values maintained in the memory that is larger than the averaged measured power consumption value. compare averaged measured power consumption value to the plurality of power consumption values maintained in the memory; and select an operational time corresponding to a power consumption value of the plurality of power consumption values maintained in the memory and closest to the averaged measured power consumption value or to the smallest power consumption value of the plurality of power consumption values maintained in the memory that is larger than the averaged measured power consumption value.