One of main design issues for a sensor network is conservation of energy available at each sensor node. To increase lifetime of a sensor network, we can organize the sensors into disjoint sets so that only one set is active at a time. The lifetime of the network increases proportionally to the number of disjoint sets. In general, sensors are randomly scattered in the monitored area, thus the number of disjoint sets is significantly smaller than in the ideal case. In this paper, we propose a way to increase the number of disjoint set using mobile sensors. We organize sensors into disjoint sets using the heuristic proposed by Sljjepcevic et al.. Then, we rearrange mobile sensors that are not included in any set. The rearrangement process consists of two phases. In the first phases, we identify the fields that are not covered by any of the remaining sensors. Then we identify the locations from which mobile sensors could cover the fields. In the second phase, our proposed heuristic selects sensors to be rearranged and locations where they will move to. This selection is made by considering the coverage before and after a mobile sensor is moved. Our experiments show that we can effectively increase the number of disjoint set with a small number of mobile sensors rearranged.