I see you have a Pioneer 111L
Now I don't know tons about audio but I know what you can do to back music cds up onto DVD-R. I would recommend you copy your cds into image files using clone cd. Clone cd makes exact copies of just about anything and it should be fine for music also as I have used it without a problem for this in the past. I am currently doing this with my PS1 games also.
So you put all your images into folders etc etc. You could fit at least 6 or 7 FULL sized CD-R images onto one DVD. I would then use Nero to make a data dvd and burn them all like that. You would easily back up about 150 or more non compressed audio CD images with 25 DVDR or less.
DVD longevity is just as good as CD-R and it's more durable so there's no reason not to use it. Just like any media though, good quality ones last longer.
I recommend using verbatim. Verbatim sell 8x -R discs which are MCC02RG20 discs and are very stable for archiving. They also sell this media with "Video Gard" protection. This makes the recording side much harder to scratch so combined with the stability of this disc, it would be ideal for storing all important data. I currently use the video gard discs for my PS2 backups and they work very well.
Good news is that I have a Pioneer 111L just like you and it burns the above mentioned discs (Verbatim -R 8x) perfectly at 4x,6x or 8x.
Of course to be even safer you can also make a secondary DVD backup onto different media, Taiyo Yuden are said to be very good also, plenty of people recommend them but personally have not used much of their DVD media.
That's my 2 cents, hope I helped