I just finished fitting 7 audio CDs, paranoia-ripped and FLAC-encoded, onto a DVD+RW media. Used only slightly more than half of the DVD space (4.4GB).
This concludes the pilot session; I'm officialy starting an enhanced CD backup process. :D
Estimated space saving: 1000%. Estimated loss of audio quality: 0%.
Thanks to sherl0k for inspiring me. :D