It is all about risk tolerance. If you make the change for $180, you are done and on the flight you want. If you do not, it is hanging over you until it does or does not happen and if it does not, you arrive after a red eye. Nobody here can tell you what $180 means to you. If it means the difference between losing your house to foreclosure, I would say you should chance it. If this is a round of drinks after work, it's perhaps an easier call.