Oh, potential sources of damage...heat, moisture, dirt, dust, cigarette smoke, strong magnetic fields, nuclear weapons, radiation, bacterial decay, proton decay, entropy, existence.
Seriously, though, if you are that concerned about them, a backup procedure like what Petro recommended is a good idea. VCDs aren't as vulnerable as a VHS tape is, though you still need to be careful about not scratching the disc.
Another way: just keep them in a somewhat secure location. You don't have to get a hermetically sealed, sterilized box, but anything that does a decently good job of protecting tapes from most heat, sunlight, and contaminants will ensure a good lifespan for those things.
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