Gift cards make great stocking stuffers — just as long as you don’t stuff them in a drawer and forget about them after the holidays.

Americans are expected to spend nearly $30 billion on gift cards this holiday season, according to the National Retail Federation. Restaurant gift cards are the most popular, making up one-third of those sales.

Most of those gift cards will be redeemed. Paytronix, which tracks restaurant gift card sales, says around 70% of gift cards are used within six months.

But many cards — tens of billions of dollars’ worth — wind up forgotten or otherwise unused. That’s when the life of a gift card gets more complicated, with expiration dates or inactivity fees that can vary by state.