I have always "monitored" my flights. I had a major change on a trip to Dominican Republic a couple of years ago JFK-MIA-LaRomana (rerouted to SJU instead of MIA which was actually a good thing).

my TA made the arrangements. American Air never notified her. I found out by accident (and this is when I started monitoring flights more closely.).

having said that I think I will check my Jet Blue flights for Sept 20 JFK-AUA and 28 AUA-JFK. Airlines are notorious for cancelling early flights in a day if they have a second flight (AA did that on the JFK-CUN nonstop a few years ago - cancelled the 8a flight and left us with a 10:30a flight.)