Jetstar has changed the flight times for an upcoming trip in February and the new times are less than 3 hours, however, they really don't work with what we had planned for the rest of the trip.
Are there any thoughts or tips on cancelling these flights for a refund if they don't automatically meet Jetstar's requirements, ie more than 3-hour difference?
Yep as long as the arrival time is different by 3 hours even on starter fare. 4+ in my case they changed our perth direct flights to flight going via melbourne this added 4 hours to our trip. So opened up a online chat session and 24 hours we received our refund vouchers just in time for japan return for free sale, we booked 3 tix to tokyo return for much cheaper than going to perth.