In this paper we describe our experiences in building tools for accelerating maintenance of existing large telecommunications software. We discuss how various maintenance activities can be accelerated by providing developers with the knowledge of the core scenarios of the system, which approximate the intended use cases. We present a static approach to extracting scenarios as source trajectories, by navigating through the source code and capturing the source statements as events. We describe our PathFinder tool for static capturing of scenarios. The possibility of static capturing of the core scenarios and their representation as MSCs have benefits in retaining expertise about existing software, in training new personnel, in focusing understanding of legacy software, performing architecture reviews, and in architecture analysis of existing systems. We believe that this approach can contribute to closing the gap between tool support for forward engineering in the so-called "green-f...