First, some recommended reading:
Quoting from the CLIR.org article:
...the three basic types of CD and DVD discs-ROM, R, and RW and RAM-each
use a different data layer material (molded aluminum, organic dye, or
phase-changing film, respectively). Deterioration of this material is
the primary cause for disc degradation and, ultimately, “end of life”
for the disc, assuming proper physical handling.
From the section specifically on -R media in order to set baseline expectations:
Manufacturers claim that CD-R and DVD-R discs have a shelf life of 5
to 10 years before recording, but no expiration dates are indicated on
CD-R, DVD-R, or DVD+R packaging, nor are there published reports of
tests to verify these claims.
So expected life for -R media is 5-10 years. Now what about -RW media?
RW and RAM discs are generally not considered for long-term or
archival use, and life expectancy tests are seldom done for this
medium. Rewritable discs use a phase-changing metal alloy film for
recording data and aluminum for the reflective layer. The alloy film
is not as stable as the dye used in R discs because the material
normally degrades at a faster rate...
To summarize: -RW media, in order to BE REwritable (rather than the write-once -R Recordable disks) uses materials that degrade more quickly than -R, and even longer-lasting -R media are only noted to be good for between 5 and 10 years. You're obviously well past that now, and that's sad, but it's also far too late to do much about it.
The articles contain more helpful information about HOW to store various media in order to prolong their lives and maximize data stability, which may be nice to know for your own long-term data storage needs, but is not going to help you or your friend now.
A professional data recovery service may be able to use specialized tools and equipment to have a better chance at recovering the data, but there is never a guarantee of this, and the costs are often high.
