I've stopped using DVD-R/CD-R's long ago... it's actually cheaper per GB to just get an external USB enclosure and a big fat hard drive.

(it also helps to have an old Linux box nearby jammed solid  with disks configured in RAID 5  and running Bacula... ) I figure between the two additional copies, I'm set ...at least until I can grab hold of an LTO-3 tape drive (800GB compressed per tape) and a couple of blank tapes.

(then again, even an old DLT IV drive would work at this point (80GB compressed per tape), and would actually be cheap enough media-wise to be practical).

/P