I thought the layers separate and they are not a good long-term storage medium. Aren't DVDs supposed to decompose after some time? Or is that only true for CDs?

I thought the layers separate and they are not a good long-term storage medium. Aren't DVDs supposed to decompose after some time? Or is that only true for CDs? I'd rip them and put them on new hard disks from time to time. AFAIK, that's the best long-term storage strategy for most people.