1) Get a second harddrive and make daily to weekly backups of your main drive - once your collection size increases you'll get dizzy recovering data from 20-50 DVDs, perhaps only to find out that one of them has disc rot and ends up useless. 2) Instead of using a rather proprietary tool such as DVDisaster I would recommend using Par2 Parity-files, which also use Reed Solomon algorithms to generate redundancy data. At 15-20% this can be read by many tools and recovered quickly, not only from DVDs but also if you have a bad sector on your harddrive that damages an audio file.
Regarding PAR2. The only GUI tool for Windows Quickpar has no multi-threading support and it also does not support sub-folders, AFAIK.
I have bought a NAS-solution...
DVDs are much less reliable than HDDs, not to mention their worse price/capacity ratio.
bluray is simply not an option, disks are way too expensive, writers are of bad quality, hard to find, and even more expensive.
or if you're really maximalist, you can set up a NAS with raid1 and 802.11n, for example.
Keep it simple (KISS):Its a backup like any other. Don't worry about bit rot or corruption too much, Avoid RAID / DVD . Just backup on a spare drive . Having a yearly snapshot on an additional drive can provide extra security. The drives can even be 80gb models from used PC's - the chances of 2 ~ 3 drives going bad at once is next to zero. In short just backup your windows profile that should contain your flacs or in unix type OS your /home
If you're backing data up remotely over the internet, make sure to keep a close eye on how much you're backing up. Some ISPs will deny you service if you use too much bandwidth.
Personally I've given up on the optical medias. They degrade rather quickly - Some faster than others though. I have much more faith in a secondary harddrive...