Keep an "eye" on this optical storage | Computerworld Blogs:

One of the problems with new technology is that its Longevity can only be theorised about, not proven 'in the field'.

Like the author of the linked article, I like optical media for archival storage - cents per gig, it just makes sense - and a half way decent DVD jukebox compares favourably in price to a tape library with similar capacity.

But the longevity is an issue - not only of the media, but of the equipment used to write it. Are DVD burners designed with the sort of usage that a backup system sees?