Thanks.
I actually do have the data backed up more than once. Both on hard-disks and DVDs.

This doesn't help much though, since its enough that the file gets corrupted on the main copy, to propagate the corruption to the other copies. On occasion, I stumble onto a corrupt image and look it up in the old copies. This happened too many times before, on various disks.

I want to be absolutely sure that such cases do not occur since this data is precious for me.
Surely there is a better way.