Do the codes for the CE DLC expire?

Right now I currently own From Ashes, Omega, Leviathan, Citadel, the appearence pack and weapons packs and the MP DLC. Basically, the only one I don't have is the Collectors Edition DLC.

If I were to find a factory sealed copy of the CE, would I be able to use the code to download that last bit of DLC? Because I read somewhere they had an expiration date on them (anyone who still has the code slip and could verify this would be very helpful).

Thanks!