Burnt optical media isn't designed for long term storage (CD's, DVD's and Blurays) aren't designed for long term storage. Even the high quality discs don't last very long. In my experience, within about 10 years, even if you store them in an air-conditioned environment, disc rot starts to set in. We have archives at work going back to about 2006-2008 which are completely unreadable.
You can get "archival quality" discs, but be prepared to pay through the nose for them.