I seem to read different things about this: one source will claim DVDs are much longer lasting, and the next will say the same about CDR's.
So I'm led to ask -- how do they really know?? The damn things haven't been around all that long.
I'm with Saab D about one thing, though -- multiple backups on different media. In my case, CDR's plus external HD. And any CDR over 5 years old gets a new copy made.