The deployment of multiple sinks in Wireless Sensor Networks may provide better reliability, timely communication and longevity, depending on the routing strategy. Moreover, geographic routing is a powerful strategy to avoid the costs related to maintaining high network knowledge. In this paper, we present a Geographic Multicast Routing solution (GeoM), focused on the latency and network lifetime trade-off. Our solution considers a linear combination of network metrics during the decision process of the next hop. Packets are forwarded to all sinks, and duplications are defined on the fly during the forwarding. The network lifetime is addressed with an energy balance strategy and a trade-off between progress and energy cost. We make use of the maximum energy consumption as an indication of the network lifetime. Simulation results show that GeoM has an overall better performance than the existing solutions, with improvements of approximately 11% for the average latency, and 54% for the maximum energy consumption.