I find it easier to book these segments with sequential dates booked well in advance (but obviously not the date you are actually intending to travel) and change later. Save all that hassle.

e.g. Last year in Feb I booked a LONE4 with travel dates USA/EUR in June and Asia/Oz in Nov/Dec.

In July a simple call to AA resulted in the Asian segments being re booked for April and Oz in May.