I saved all my XMP files out and am saving them with the couple-dozen PSD's and the original NEF's. I'm also archiving a copy of the catalog and a demo version of the software.
I'm hoping that will protect me in the future if/when I need these again... but we won't know until a long time from now.
Misc personal stuff: http://www.joefederer.com
Minneapolis / St. Paul Wedding photography @ http://www.federerphotography.com