Along with the millions of gift cards having been found in Christmas stockings or unwrapped from under the tree, consumer advocates are offering advice: Use the cards; use them quickly and completely.

The main message is to treat the gift cards as if they were cash. Do not toss the cards in a drawer or where they might be lost or forgotten. Another bit of advice is to use them, and don't leave any unused value on the card. That's just a nice profit for the bank or retailer issuing the card.

The undeniable convenience of gift cards is a big reason for their popularity in recent years. But consumers also should be aware that the money left unspent on cards, either because the cards are lost or because a small balance remains after a purchase, is expected to amount to $5 billion this year.

The problem used to be worse. A few years ago, the unspent balance was almost double the amount expected this year. But media coverage has helped consumers learn about the secrets of the gift card industry and become more aware of questionable practices like expiration dates and monthly service fees that drained value from the cards over time.

In the past year or two, most of those questionable practices have ended or become rare. Many retailers already have eliminated expiration dates or monthly fees ahead of new federal regulations that will become effective in 2010.

Experts say that, on average, between 5 percent and 15 percent of a gift card's value is never redeemed. For some businesses, that unspent money is a major source of profit — sales revenue without any goods or services being exchanged.

For consumers, the unspent money is a loss, not much different from tossing money in the trash.

For that reason, consumer advocates suggest using a gift card fairly soon after the holidays. That way, the cards are unlikely to be misplaced or lost.

Experts also suggest finding something to buy with the gift card that costs a little bit more than the value of the card. That way, even though some extra cash will have to be handed over, the full value of the gift card is used by the person for whom it was intended, rather than being pure profit for the bank or retailer that sold the card.

Not all retailers report the value of unspent balances on gift cards. But it's instructive to note that Best Buy says it kept $38 million from unspent gift cards or unused balances last year. The figure at Home Depot was $37 million. Other retailers probably have similar experiences.

And early this year, the bankruptcy of Circuit City meant a total loss for many holders of that store's gift cards. As rare as a retailer bankruptcy might be, consumers can eliminate the risk by using gift cards quickly rather than holding on to them for months or years.

Using a gift card promptly and fully is the best way to get the complete value of the gift and to get what the buyer of the gift card intended. Leaving a card on a desk, in a drawer or not spending the full value is the worst thing that consumers can do — it benefits the bank or store, not the gift card recipient.

So the experts suggest keeping gift cards handy in a wallet or purse, use them quickly, and make sure to use 100 percent of their value.

Gift cards are a wonderful convenience and can be a thoughtful present, but only if they are used.