

This is terrible advice. Most writable DVDs degrade quickly, even if they’re stored away from sunlight and heat. Every single one of my burned DVDs from more than a few years back is completely unreadable.
Update: I missed the very important line about M-DISC. This is critical. I can’t vouch for M-DISC personally, but most other optical media is garbage for archival purposes.
Yes, they were organic dyes. At the time, those were the only kind. Maybe it’s gotten better over the years.