I've been asked several times. And always when I plan to stay 90 days or more. Sometimes they will ask to SEE it. Marko has an interesting method/Spirit airlines. If you book a REFUNDABLE ticket you can do the same thing, but then you are laying out/putting on your credit card the more expensive ticket. Southwest gives free changes but it goes to your account as a credit to use in the future (or get a REFUNDABLE ticket and cancel, then book the flight/date you really want)