Sound quality degrades after 6 months

[JBMouse]

I have burnt lots of back up music cd's to us in my car, but now after about 6 months some of them sound terrible all of a sudden, with lots of crackle and hiss with the music. Why? They are all low cost, about 20p to 25p each sold on spindles, with no manufacturers name, and I have put full face labels on them all, so what is wrong? cheap disks? label glue reacting or what?
Answers please!!
JBMouse

[EMPiRE]

Most likely the quality of these "low cost" CD-R's is plain bad... If there are too many errors on the CD-R the error correction can not fix this anymore and this results in crappy sound.

If you are also using these CD-R's for data then you get too see errors much faster than on Audio CD's

look here (a bit outdated but still valid):

http://cdmediaworld.com/cd_quality.htm