You could stick the master versions on an external HDD somewhere and when Blu-Ray media/burners/etc becomes more prevalent, there y'go! For now, DVD-9s would be great.
P.S. Does anyone seriously know why DVD-9s are still so expensive? Is it just because they can charge whatever they want? Are they harder/more costly to make? It just doesn't seem reasonable to me to charge ten times more for the same sort of basic disc.