Burned disks, you'll probably lose some over 30 years, i've lost a few in 20 years, most are still readable.

Poorly pressed disks, you might lose one here or there. I had a two where the aluminum was poorly sealed and flaked off the label side.

I have hundreds of DVD's in the 20-30 year range and have never had a problem reading any of them that weren't scratched save the couple that were lacking in top lacquer.