Maintenance will be critical to digital libraries, especially those that promote broad access to diverse, informal materials. If ignored, maintenance issues within the digital library -- especially those relating to its materials -- will threaten its usefulness and even its long-term viability. We perceive the maintenance problem to be both technical and institutional, and this paper considers the maintenance of the digital library as both institution and technology. The paper examines collection maintenance from several vantage points, including software architecture and the type of collection, arguing that digital libraries that contain informal and dynamic material will have substantially greater maintenance problems. The paper ends with an examination of potential technical solutions.