I guess that was just an instance of the "Survivor Bias". I burnt hundreds of CD-R/DVD-R/DVD-RW disks from a various of vendors(mostly Sony, TDK, Verbatim, Koda

I guess that was just an instance of the "Survivor Bias". I burnt hundreds of CD-R/DVD-R/DVD-RW disks from a various of vendors(mostly Sony, TDK, Verbatim, Kodak, maybe some other brands which I could not remember clearly, each brand should be at least 50 as I had always bought 50 pack tubes.) around 15 years ago and left them untouched for around 8 years when I needed to retrieve something from those archives. So I decided to check the health of those disks which was quite disappointing. I simply tried if I could read the first 10 disks in each tube and it turned out, for a brand, all 10 were not even able to be recognized. Other brands performed from 3, to 8 in 10 disks could be read. That was just simply trying to read, so the integrity of the contents were not checked at all. The only good thing was that I managed to locate what I was looking for and it was in RAR format which validates the hash when extracting, it was good. So I immediately tried to move those I wanted to keep to HDDs and the loss rate was over 50%, and for those recovered, I didn't have much confidence regarding their integrity neither as no checksums saved. So basically I wasted lots of time and money by choosing optical drives as archive media. In the mean time, all files I left on HDDs were perfectly fine. This might be another survivor bias too.