In this paper, we develop and evaluate a new concept of adaptive optimal redundancy to efficiently provide wireless sensor network (WSN) users with QoS-aware information services. Our approach to satisfying application QoS requirements while maximizing the system lifetime is to determine dynamically the optimal level of redundancy at the ldquosourcerdquo and ldquopathrdquo levels in response to network dynamics and query QoS requirements on a query by query basis. We develop a mathematical model to analyze the performance characteristics of our proposed solution. The obtained results show that dynamically and adaptively identifying and managing optimal redundancy for per-hop data delivery lead to satisfying query QoS requirements in terms of reliability and timeliness, while maximizing the useful lifetime of WSNs. We validate the analytical results with extensive simulation.