This paper proposes a new measure for network performance evaluation called topology lifetime. The measure provides insight into which one of a set of topologies is likely to last the longest before more capacity must be installed. The lifetime measure is not single valued, but considers growth as a function of a set of demand shifts (perturbation). One network may be better able to support a uniform growth in the traac, while another may support more growth when unexpected shifts in the load occur. The ability of a network to support unexpected changes in load is becoming more important because of (1) current practices for installing ber optics cables, (2) recent advances in dense wavelength division multiplexing (DWDM), and (3) the increasing popularity of the Internet. The lifetime measure is applied to several topologies; a dual ring, a chordal ring, a Manhattan Street network and an hierarchical network. In this paper, our objective is to show how to apply the measure and to explain certain implications for comparisons between networks. We expect this measure to be useful both in the construction of new networks and in selecting between new links that may be added to an existing network.