You should check pricing on separate legs for your trip. I have deboarded/reboarded the same plane at the mid-point on a two leg trip before, with enough time to go to the restroom and grab some coffee to take back on the plane with me. I actually had a separate boarding pass for the second leg, because it was cheaper to book the two legs separately even though it was all on the same plane. Obviously this isn't always the case, but its worth checking and it eliminates any hassle you might face. Of course you will lose your seat under this scenario, unless you want to risk leaving an item on your seat to "save" it and hope that it is respected.