Back when I ripped my 600+ CD collection to mp3 I made two sets (about 50 CD-rs each set) of mp3 data discs. One to be stored as an archive set and one to travel with me as I was on the road about 300 days a year. I listened to them on a CD/mp3 player, as HD mp3 players at the time didn't have near the capacity to store the entire collection and my laptop then only had a 20GB HD. The archive set I marked with Sharpies. The travel set I made adhesive labels for, with artist & album info and album cover art. During the label making process, some of the labels had minor mistakes printed on them (like the album cover art images weren't in the same order on the label as the files for each album were on the disc). Two of those labels were already applied to the discs before the mistakes were discovered. For those two discs, I stored the ones with mis-printed labels as the archive copies and made corrected labels which I placed on the discs marked with Sharpies and put them in the travel set. Both sets used the same brand of blank media from two 50-packs purchased at the same time. Since I burned two copies of each disc as I went along, the first package of blanks were used for both the archive and travel copies of the first 25 discs in each set, and the second package provided the blanks for the second group of archives and masters in the set. The archive set has been stored in a dark, cool, dry place since that time, except for when I sometimes needed to copy a replacement disc for a damaged one in the travel set (usually due to scratches from dust and vibration, etc... or so I thought).
Recently I acquired a 160GB external Hard Drive and decided to transfer all the data files from the archive set onto the HD. Guess which discs were the only two in the entire archive set to experience read errors during the transfer? Just as most reports on the subject have noted, the data near the edge of the discs was the most degraded. Even when slowing the CD reader down to 1x, several of the final tracks on those two discs were unreadable, and I had to re-rip from the original CD's to complete the collection on my HD. I then checked randomly selected discs from the travel set (all with labels) that I don't use much anymore since my job now doesn't require the travel and found a good number of them with read errors near the edge also. While sunlight, humidity, scratches etc... may be used to explain the problems with the travel set, the two discs with adhesive labels in the archive set were never exposed to any of those environmental factors. The ONLY difference between those two and the other archived discs were the adhesive labels.