I tend to have multiple AA flights booked at all times, generally 4-5 months in advance, and I’ve had rampant schedule changes over the last 3 years. It is not uncommon for itineraries to be changed once and then changed again over the course of several months. This can involve anything from minor flight time changes (which are usually accompanied by flight number changes) to outright cancellations/re-bookings. It has in many cases worked to my advantage, in which an inconvenient flight that I had to book because that was the only award available gets changed so much that I am able to shift myself onto a much more convenient flight that didn’t have award seats when I originally booked it