One of the biggest disadvantages of large scale wireless sensor networks lies on the complexity of logistics involving selective replacement of sensors that have ran out of energy. Fortunately, efficient power management schemes provide some relief as they are designed to extend network's lifetime and thus reduce the need of external intervention. In this paper, three centralized and one distributed efficient coverage algorithms are proposed to obtain an improved monitoring quality over time. Simulation results evidence a moderate yet encouraging performance of the distributed scheme and an excellent behavior of the centralized ones