I noticed one thing that jumped out is there is NO mention of storage in CD wallets?
There can be many reasons why others had failures in wallets. We do not know how they labeled their media (stickers, harmful ink/solvent..etc), we do not know the condition how these were stored or where they were stored. We don't know the brand or media code used as well.
I never have used labels since I did not want to be out the expense for that or the ink to print them on. They are just used for my own use so I don't need to impress myslef. I have always used a thin tip permanent marker....not those big fat tips...since the less ink on the top surface the better. I have always wrote on the top side and not around the hub area where there is no data.
I also have not bought super high quality wallets either and still after 15 years (knock-on-wood) I have no problems.
I am new to the DVD world so don't have many of those yet but that collection is growing.
I agree there is NOT enough evidence out there to remove the idea that CD wallets are the culprit for degrading DVD's. I have only read in a few posts here and there about this issue, but many variables were not even mentioned. One idea that may contribute to this matter is the potential of that soft material to absorb mositure from the air and cause damage that way.
I would say using CD Wallets for 15 years is a good test of time, wouldn't you?