I have CDs I burned over 7 years ago that are still perfectly fine.. even with the scratches they've accumulated over the years.
It might just be because of the crappy material that they use. Perhaps it's so cheap just for the fact that it's material that corrodes after a year or more.
I generally buy 100 of a well known brand (Philips, Sony, etc..) for around $15-20.
My concern right now would be with DVDs since that's what I primarily burn anymore
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