Is it possible that they wait to notify you at a certain point (2 weeks?) before your departure? I usually watch my flights that are months out and the times will change 15-20 minutes sometimes and then even change back again! If your flight is a ways off, maybe just check a few weeks before? Now I did have an F9 flight actually cancelled once and I noticed it and called to rebook. I don't know when they were planning on letting me know that! I think that if the flight is actually cancelled, they should notify you right away, no matter how far out.