One thing you might want to check into is to see if there has been a schedule change on your reservation. CO will change your flights once for no charge if it causes a problem. However, there are two stipulations - one, there actually has to be a schedule change - don't call and say there was one (they will check for as long as necessary). Two, the flight that you are booked on must be moved later (that way you have an excuse for going earlier - if the flight was moved earlier than they would only move you to the later flight).

Good luck.