For those that have never heard of it before, M*disc is a recordable media (currently DVD only) that uses a ceramic layer rather than an organic dye and metal foil.  Ordinary recordable media has a very short lifetime because the dye denatures and the metal foil oxidizes.  M*disc drives use a higher powered layer to burn holes into the ceramic layer, so they should be good for a long time.  Estimates are currently up into the 1000 year range.  I figure mine should be good for 50 years or so.