Network lifetime is the ultimate objective in evaluating the performance of Wireless Sensor Networks (WSNs). To assess the network lifetime correctly for a particular WSN deployment, utilizing realistic abstractions for modeling various aspects of system components are crucial. The overwhelming majority of the studies on the WSN lifetime maximization utilize well known theoretical path loss models like the two-ray model, however, such models do not lead to realistic path loss results. In this study, we formulate a detailed link level model of WSNs utilizing Mica2 motes and, based on the link layer model, we construct a novel Mixed Integer Program (MIP) to analyze the effects of path loss models on the WSN lifetime. By exploring the parameter space through numerical evaluations of the MIP model, we characterize the impact of path loss models on the WSN lifetime.