This subject has been dealt with at length previously, in fact I wrote a response to a similar question in 2006 that "won" that weeks response award (it was the 1/27/2006 column, if you want to look it up).
In a nutshell: You are PROBABLY being paranoid.
The best information available (and it's definitely somewhat limited since CD-R has only existed now for 14 years or so) is that QUALITY optical media burned on a quality PROPERLY WORKING drive, will last at least 50 years and some estimates go out to 300 years, based on the best avaialble lab work and analysis (it goes without saying that no one has been able to test even 50 years in real world conditions).
Now, however, a bunch of caveats:
1. Media: There is good media and there is junk media. And there are dozens of different dye formulations in at least five major dye families (if you care, they are Cyanine, PhthaloCyanine, Metallized Azo, Advanced PhthaloCyanine and Formazan). These all have significantly different characteristics (they WILL have different lifes), and each of them can be made into a "quality" or a "junk" media of that type. I guess it goes without saying that junk media, of any type, is just that .... junk.
2. Drives: There are good drives, there are bad drives and there are good drives that have become defective. It is my personal opinion that a lot of the problems that we have are caused by drives whose laser output power levels are below spec. That can happen even to a high quality drive that was once good (it can also happen simply because the optics have become dirty). So the media isn't heated to the proper temperature, the dye doesn't fully change it's reflectivity and you get a burn that consequently has poor long term stability. So the moral of this story is that everyone who has an optical burner should have a laser power meter and use it regularly (just kidding .....).
3. Storage and handling: This, too, effects life. Temperature, humidity, handling, storage type (it's better to store discs vertically; DVDs should not be flexed (including as in removing them from a case), scratches can do obvious damage, etc. etc.
So you put all of those factors together and they all impact the life of your media. The estimates of 50 to 300 years were for quality media properly burned and properly stored. There is no absolute guarantee that any of us real world users will meet any of those critera much less all 3.
So what is the bottom line? Here is my conclusion:
All indications are that properly burned optical media will last for decades.
However, as all kinds of backups do fail, I ***ALWAYS*** have multiple backups. And I think that is one rule that applies for all backups of all types. One backup, even two, is NOT enough.
***NEVER*** use "RW" media (CD or DVD) of any type for anything that you plan to keep. Only use "R" media. Sorry, RW media just is NOT stable, I've had too many bad experiences with it in my 40+ years in the computer industry (only 10+ dealing with optical media, but that's enough for me .... I've seen a years long clear pattern emerge).
After using a drive for a while, and after using media that it has burned in other computers with other drives, you will get a sense of whether or not the drive is reliable. Pay attention to that; signs of unreliable operation (especially problems reading discs later, either in the same drive or other drives) should not be ignored. FWIW, I've had the best luck with Samsung (now TSST) and Pioneer and, frankly, much worse luck with almost all other drive brands (and I build and service computers, and this is based on hundreds of drives that I've dealt with).
Also, you mentioned "shelf life" in your query, that really would refer to the time BEFORE the media was burned, the time between when you bought the media (really, when it was made) and when you burned it (the time subsequent to burning would be the "archival life"). Shelf life is limited, optical media should be used with 5 years of it's date of manufacture, although in general we have no way of knowing when the media was made, but usually it will have been bought within a few months of manufacture.
Hope that this helps,