This paper describes our experience of developing a new system (Greenfield development) after continuously extending an existing one (Brownfield development) for a long time. Our experience however does not seem to be unique to our context. Complex systems tend to live longer and be continuously updated to stay relevant over many years. With this longevity there is a risk that there are few, if any, leaders who have experienced a previous transition from Brownfield to Greenfield development. The paper characterises how development changes and illustrates the organisational challenges during the transition. The paper also presents some indicators of an approaching transition to Greenfield development, together with some management strategies for preparing the organisation for a successful transition. A key message in the paper is that an organisation optimised for Brownfield development is inherently unsuitable for the challenges in Greenfield development.