Organizations have been confronted with fast moving developments in the Information Technology (IT) sector over the past decades. Many new technological paradigms have emerged and left a landscape of legacy in which more and more money is spent on maintaining this landscape at the expense of innovating. Especially where business requirements put time pressure on the evolution of the IT landscape the decision whether to continue and maintain legacy systems or to decommission legacy systems in time has become a huge challenge. We formulate a set of propositions influencing the decision to decommission or continue legacy systems. This set of propositions is derived from literature and interviews with high level managers of organizations. Software characteristics, development methods, dependency of systems, lock-in, system complexity, new technologies and system ownership influence the decision whether to decommission or to maintain a system. We conclude this paper by proposing a methodology that helps organizations in finding the right balance between discontinuing and maintaining legacy systems.