Energy efficient routing protocols are an active research area in Wireless Sensor Networks (WSNs). Like prior research works in efficient-efficient routing protocols, we enhance the LEACH cluster-head (CH) threshold mechanism. Our approach mainly focuses on the idea of maximizing the network lifetime on the basis of CH nodes remaining energy levels. In LEACH, CH changes occur during every round of the network irrespective of their energy levels. In this scenario, we propose an energy threshold function as well as an optimal CH threshold function to specify the dynamicity of the CH, whether to change the cluster-topology often or not with the consideration of its current energy levels. In this regard, simulation results show that the proposed mechanism can maximize the network lifetime effectively and delivers three times more data messages while comparing with the other known energy-efficient protocols from the literature.