Hard drives fail more often than another computer component, at least the old-timey spinning hard drives. SSDs are better by far but I wouldn't trust important files to any single hard drive for long term storage.

Optical discs don't have that problem at all. They will be good as long as you keep them in a non-hot place out of bright lights. Heat and UV light and scratching are the enemies of optical discs, but they can all be avoided for as long as you care to keep them safe.