The accounting entry at purchase is to recognize the cash as an asset and the obligation to honor the gift card as a liability in equal amounts. There is no sale recorded until the gift card is redeemed.That's pretty much my understanding, I think they may be counted for as sales, but then you need to account for them as a future liability. However these cards are often only valid for a set period....after which I guess you they cease to be a liability and then you have free money.
As for the expiration, this is highly dependent on state law. In many/most states, gift cannot expire, although there can be a "non-use" fee of a reasonable amount that can erode the value. I don't believe Disney has such a non-use fee, perhaps because those fees are illegal in Florida (I don't know). For cards that do not expire, virtually all states require that, after a period of time, the issuer "escheat" the remaining funds by transferring to the state the remaining balances. Owners may then apply to the state for reimbursement.