We live in Illinois where flying during the winter can be iffy because of ice, snow, etc. We always arrive a day early, just to be on the safe side.
Don't forget to get travel insurance. It could come in very handy if you experience flight cancellations or delays due to weather or other unforeseen circumstances.
I agree with Lisa. Pay the change fee and then you can relax and not have to worry about rushing or delays.
Have a great cruise!