i was doing some research on long term archive methods last night, read about the different ways cd-r and dvd+-r discs degrade over time. this morning i found what appears to be a pretty awesome error correction program - dvdisaster.
edit: here's the link -
also, a good article discussing archiving to optical media -
it's free on sourceforge and it's designed to add ecc info to your optical archives, let you know when they're starting to fail and recover from errors so you can move to new media when the old media starts to fail.
i'm using it for the 1st time right now - i'll report back w more info as i get more experience w it.