For a library this is an important advantage. There are significant disadvantages of this strategy. Sometimes the loss is identifiable and made very clear, and worryingly sometimes it is not. It is this potentially unknown data loss that makes migration somewhat problematic. Refreshing does not imply ensuring the material is kept useable - it is only the transfer of a bytestream from one medium to another.
Migration focuses on keeping the material functional with new technology.
The Open Archival Information Systems Reference Model has been developed by the Consultative Committee on Space Data to provide a conceptual framework and reference tool for defining a digital archive. It describes a specific functional model of both people and systems requirements for implementing a digital archive. Indeed the model could also be applied to a non-digital archive. The OAIS model has been accepted by the International Standards Organisation and the Cedars project has provided a demonstrator project based on it. The importance of OAIS to the archiving community is undeniable but its usefulness to research libraries and archives largely unexplored.