I have never done online check in for SW before, and I'm a little confused. I just hit the online check in button. It shows our boarding passes, and gives me the option to print them. If I print them and my printer messes it up, can I then reprint them at the airport--or is it a one sot deal? If I don't print them now and wait until I'm at the airport, will my boarding number change or remain the same?