I've kept discs in both disc wallets and in spindles. The spindles are mostly kept in a cupboard or under my table. I've done this for a year and the discs are still fine. They pick up a few bits of dust but give scans about the same as a year ago after I clean the disc a bit.
The ones in the disc wallets don't seem to be doing so well. I've got a few scratches on them and I scan see that the quality of the scans compared to a year ago has deteriorated slightly. The scans are still good, but it is obvious to me that the disc wallets aren't that great for storing DVD discs.