I export each shoot I process as its own catalogue with previews. I then burn that catalogue and the RAW files to DVD using any DVD burning software. After a few months, when I know I won't need them I delete the RAW's and 1:1 previews from my main HDD. That way the thumnails are there for the DAM functions.
This is an addition to my general catalogue backups, so I now have two copies of each catalogue if needed.
Gordon