Time for a round-up:

  • Always keep the original bitstream of a digital resource, no matter what application it was created in, proprietary or not.
  • Never let the user consult the original. She can consult a copy. This copy does not have to be in the same format as the original, unless the user herself demands it.
  • When the time comes to migrate the data, migrate it to an open, XML-based format, if possible. But still keep the original.
  • Keep metadata separate from the original data object.
  • Store everything on a dedicated server, with backups, rather than offline media.

And remember the two laws of digital preservation, which follow irrefutably from the fact that no one has or will ever come back in time from the future to tell us what will work:

  • No one knows anything.
  • No one will ever know anything. 

That’s the position today, at least.