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Terminal 2, Heathrow airport, London
Terminal 2, Heathrow airport, London
Stephen Chung—Alamy

More than 98 million Americans hit the road at some point during the holiday season last year. One thing that was true for just about everyone one of them: When it comes to going over the river and through the woods, you'll get to Grandmother's house for less if you plan your trip far in advance. But how many of us do that? When do you book? Tell us!