OP, just do not worry too much for now. The flights are five months away. If there are a few minutes of schedule change, you can move to an earlier flight if you ask nicely. A reservation agent will accommodate you. If there is no schedule change, you can try to "standby" for an earlier flight on the day of travel; for example, going to airport early enough to catch the early-afternoon flights (just check the flight status and loading to determine the flight for standby).
Good luck.