Rushbridge’s thought rather than mine, but very realistic:

“It seems to me that it makes more sense for most of us to view digital preservation as a series of holding positions, or perhaps as a relay. Make your dispositions on the basis of the timescale you can foresee and for which you have funding. Preserve your objects to the best of your ability, and hand them on to your successor in good order at the end of your lap of the relay. In good order here means that the digital objects are intact, and that you have sufficient metadata and documentation to be able to demonstrate authenticity, provenance, and to give future users a good chance to access or use those digital objects.”