I was reading elsewhere that Spirit doesn't allow you to buy 1-way tickets from some places south back to the US. Yet on their website it seems easily possible with cheap fares most of the year. Maybe if they see certain IP addresses they think you're a local and are aiming to stay in the country. This is a real problem for travelers that want flexibility - and who doesn't? If you're gone for months you have no idea when you'll want to return. 1 way tickets are the only way to go. Of course you can buy refundable 1 way tickets so they pass the scrutiny of customs if they really get sticky - then refund them as soon as possible.