Problems with storing CDs in wallets, horizontally

Can anyone give me solid information about possible problems with storing CDs in wallets, horizontally? I keep my music collection in large wallets (224 discs, 8 per page, double sided) and stored flat because that is most convenient for quick access. I’m concerned that, long term, this may damage the discs. The advice is to store vertically but this seems to refer to discs in jewel cases and is to prevent warping. In a wallet each disc presses flat on the one below so warping doesn’t seem a danger. How about compression? In my wallets 56 CDs maximum could be in a stack. Also I don’t close the wallets. They’re not in direct sunlight, quite, but daylight might be a preblem, long term; I don’t know. These are CD-Rs, nearly all Verbatim. A problem with going to vertical storage is that pages tend to come loose from the binder rings.