CD-RW discs do degrade faster than CD-R discs. -RW media isn't optimal for long-term storage.
Of course, you can reburn these discs easily with no waste (other than your time).
Try other readers... you might be able to coax the data off the disc.
If you have any other really old CD-RW burns I'd recommend you reburn them (or transfer them to a good CD-R disc) as soon as possible.