Wow! lot's of GOOD questions there! I hope I can answer some of them for you
My discs that have failed after 7-8 years have mixed results. Some no longer can do ANYTHING, which mean most drives will spit them out at first sight, and some are just REALLY scratchy. However, since most of my CD-Rs have data on them, they are effectively usless to me either way. When I say a disc is dead, it usually means an average C2 error rate of thousands.
As for the lifespan of newer CD-Rs, well, that's really impossible to say, since they haven't been around long enough for me to do a real life age test. However, I would recommend periodically testing the CD-R/Ws that are important to you, to see how they are doing quality wise. You don't have to test them every week or even every month though, just every once and a while.
Copy the data off of that Memorex 16x-24x CD-RW *RIGHT NOW* if you value whatever data you have backed up on it. I have not heard even one report of a person having the disc work properly for them. Most people I have talked/messaged with who purchased the discs, have demanded replacements, and eventually refunds. And the disc is made by Infodisc, K-Probe is wrong. K-Probe's manufacturer identification ability is still a work in process, so take the info with a grain of salt for now
I stand behind Prodisc CD-Rs personally. Like I said, they aren't great, but they ARE good. Though their latest batch has left a little to be desired from what I've been told. Generally Prodisc is considered to be one of the safer media types.
I would suggest avoiding Memorex media altogether, since memorex buys media from MANY different manufacturers, and you never know which one you will end up purchasing. Sometimes it could be T.Y. sometimes it could be infodisc!
As for CD-RW recommendations, go for Verbatim Datalife Plus CD-RWs. They are usually made by Mitsubishi Chemicals, and are considered to be one of the (if not THE) best CD-RWs in the world!
I'm not 100% sure who made the gold memorex CD-Rs you speak of. I've seen gold memorex CD-Rs made by Infodisc, DST, and CMC, but not Ritek... could you give me the ATIP please? I could give you a better answer with that.
Regarding your Memorex 48x Prodisc CD-Rs, I'd be more then happy to take those off your hands if you don't want them anymore!
and finally, regarding CD technology versus CD-R technology. They are TOTALLY different. If you remember, when Compact Audio Discs first became available, most of them rotted within a year or so. This prompted some MAJOR improvments in the manufacturing process, and generally speaking it isn't an issue anymore, assuming you take good care of your CDs. Humidity and enviroment are major issues of course, but there have been no major outbreaks of CD rot lately amongst the pre-mastered audio discs...at least not that *I* know of. Remember, CD-Rs are good for backing things up because they are disposable. Pre-mastered CDs are made to last the test of time, but are still subject to the everyday wear and tear of scratches and dust.
I hope that helps you out!
Punch Cards -> Paper Tape -> Tape Drive -> 8" Floppy Diskette -> 5 1/4" Floppy Diskette -> 3 1/2" "Flippy" Diskette -> CD-R -> DVD±R -> BD-R
The Progression of Computer Media