My experiences with CD-R (4.35GB capacity) is that they are very reliable. I take good care of them and never touch the disc surface. I have over 100 of these and none of them have scratches or fingerprints on them. They are either stored in a typical CD rack, but are usually moved to a box where they are stored horizontally (the box sits on it's side. They are put in vertically, but end up horizontally because the box fits where it is when it's sideways.) I have pulled out CD-R's that were stored in the 90's with data on them that played and loaded up fine. I usually copy the data to my CD and view the videos there to lessen the load on the CD drive. I have never, once, had a CD-R fail to read aside from a defective CD or two out of, literally, over 100 of them that I have. No matter how old they are, they always stay intact. I always take good care of CD's, whether they are data CD/DVD-R's, video game discs or music CD's burned or otherwise. I've never had any issues with CD-R's with a 4.35 GB capacity or the 650MB/700MB ones I have, though very few of those since I usually store large amounts of data at a time.
The CD-RW ones are crap and are usually completely unreadable after a year or two or less. I don't know what it is about them, but don't use them. They are completely unreliable while CD-R's I have that were burned probably around 15 years ago have preserved the data on them as if they were just burned. I never leave CD's laying around, they always go right back into their case after usage and I never touch the "writing" side of discs, always the sides or (usually) a finger through the middle hole and one finger on the side. I find CD-R's to be extremely reliable especially if you take good care of them. I seldom use them and they aren't exposed to light. Storing them horizontally doesn't seem to matter as opposed to vertically. I've never even heard of such a difference until just looking this stuff up now out of curiousity.
My brand of choice is TDK CD-R discs with a 4.35 GB capacity. Hell, I have VHS tapes over 20 years old that still play perfectly (well, for a VHS anyway.) I think the biggest factor as far as life span with stuff like this is how you care for and handle them. Always store CD's in their cases and never leave them laying around just as you always store VHS tapes in a protective sleeve. Room temperature in a house seems to be just fine. Take care of your things and they will take care of you.
I know this is an old thread, but I just thought I'd share my thoughts. This technology has surely gotten better since the last post in this thread almost seven years ago.