LoRaWAN-based wide area monitoring systems may use non-stationary LoRaWAN gateway devices to collect sensor data. In these cases, the most suitable locations for gateways must be found, while taking into account the scarcity of radio resources and energy consumption. In this paper an optimization model is proposed that aims to address this problem. The model ensures that power drain on the most critical devices is minimised fairly, considering an amount of packets to be delivered, and can be used to plan changes of gateway locations periodically, so that the network lifetime is extended. Results show that the optimization model and proposed pipeline are adequate for the planning of wide area monitoring where in the long-run different devices will be communicating in parallel, with the same gateway or different gateways, and sharing the spectrum. The approach can also be used to anticipate any gateway rearrangement need to ensure the extension of the lifetime of the network.