Wireless sensor networks have mainly been designed for information-collecting purposes, such as habitat monitoring, product process tracing, battlefield surveillance, etc. In order to support efficient communications for such networks, many routing protocols have been proposed. However, protocol designs are out-pacing formal analysis. We propose an optimization model in this paper to bound the routing performance in terms of network information collection. We first argue that a network can only be given a death sentence when it fails to satisfy the application?s requirement and propose a more reasonable network lifetime definition. Then, the optimization model concerning maximizing information collection routing is presented based on this new network lifetime definition. Existing typical routing algorithms: MH, MTE, FA and MREP are simulated as references to validate the model proposed. Results show our model can provide a tight upper bound and thus can be used to evaluate existing and up-coming routing algorithms.