I have a CD/DVD duplication business and go through thousands of discs a year. The media, while some is much better than others, is made cheaply. Sometimes I can go through 500 or more discs without a reject but other times they can have up to a 7-8% failure rate...and that is when they are new. As someone who uses this media frequently and for a long time, I would not trust it for archiving. Also, using so many discs is a PITA IMO. At the same time, there are so many ways a HDD can go bad, and they do, frequently. As they say, and as I believe, there are 2 kinds of hard drives, ones that have gone bad and ones that will go bad. If you use hard drives and you NEED your data and you do not subscribe to this way of thinking, then you are setting yourself up for disaster. Because of these issues with both forms of media, I have opted to use hard drives for their convenience, but in a double, 2 location, RAID5 system as I explained in an earlier post. But, I know I need to add LTO (tape) backup to safeguard against file corruption or accidental deletion.
On another note, I really think it is overkill or save 24 bit and 16 bit versions of masters along with flac in 24 and 16 and final version and final flac, etc....
Just use a program that does non-destructive editing like samplitude. Then, you only need to save the original master files. But, I also save a few other versions sometimes for convenience like a CD image file for duplication for instance or mp3 for portability, etc.