We consider large-scale asynchronous wireless sensor networks (WSN) for environmental monitoring applications, where overhearing severely affects the energy consumption of the nodes. As the on-board energy resource is limited, conserving their energy is important. To mitigate energy wastage from overhearing and to improve the network lifetime, we propose multi-channel operation where each node is assigned any one of a small set of channels. We propose a game theoretic framework for solving the channel selection problem that maximizes the network lifetime. The proposed approach largely reduces the computation complexity of channel selection. Computer simulated results will be presented, evaluating the performance with this approach.