International audience; A wide range of initiatives for developing research and data infrastructures have been funded in recent years. There is a growing concern amongst the academic community to maintain the resources invested beyond the period of the original research funding. If technical progress has been made to preserve the data themselves, few thinking and operational solutions exist for the institutions that create, disseminate, curate and preserve the data. How to ensure their existence over the medium or the long-term? This paper is a case study: it addresses the sustainability issues faced by Persée, a French platform dedicated to digitized documentary heritage that was launched in 2003. Through this example, the aim is to present, in practical terms, how an organization has to adapt and to change to sustain over time. Persée tested and combined various mechanisms (technical actions, users’ involvement, organizational evolution, marketing, funding models) with reciprocal influence, to achieve sustainability. Rather than a steady state, ensuring the long term existence of a data infrastructure is an ongoing and resource intensive process.