The only way to keep long-term data is to perpetually renew it. And to test that what you have stored is in good condition without corruption.
Hear ye, hear ye!
Back up to a mirrored harddisk-based device - if you can afford it, more than one mirror disk. Do incremental backups and not simply synchronization (what good is a backup if it stores a file that became corrupted on your workstation, and you can't get back a good copy of the file?).
Ideally, you also need to backup this storage to an off-site location... this could be through a (super)fast internet pipe, or on an external harddisk that you routinely sync and then leave at a friends house/whatever.
If you can't afford to do that, I'd agree that the only guaranted long-term answer is paper.
We had a thread
about "paper-based backup" a while ago. I dunno if today's paper and printers would last as long as some of the old papyrus, though.
As for the whole DVD/HD-DVD/BluRay/whatevernextgen
, I'm waiting it out. I have a DVD collection that I'm not going to replace anytime soon, and the whole HD "infrastructure" isn't really there
yet anyway. Once I get the cash for a 1080p capable TV, I'll reconsider things... and the new format might actually have arrived then