Funny you should say that, because Frontier Airlines (our carrier) have already changed things up on us. First off, we were supposed to leave Oklahoma City for Denver at 1:45 pm. Now, It's all the way to 1:47 pm. Also, we're supposed to get into Orlando at 9:55 pm instead of 9:22 pm. Then, the return flight has changed even more dramatically. We were supposed to fly out of Orlando at 5:00 pm and arrive OKC at 10:14 pm. Now, it's been changed to an 8:42 am departure and a 3:47 pm arrival.
Schedule changes are grounds for having the ticket canceled, penalty-free, for a full refund if you choose. They just axed your last half-day in Orlando and you'll be getting up at 6:00 for the flight home if you keep that ticket. All you have to do is tell them you can't make the return flight.