Well UV light and oxidation cause disc-rot[0], so even if you leave them in their cases, they will eventually go bad. Therefore the only choice is keep them in a temperature and light controlled underground environment. Self-burned media tends to rot even faster.

And my point was mostly that if you're DJing with them, it's hard to keep them in pristine condition.

[0]https://en.wikipedia.org/wiki/Disc_rot