Notice you plan flying SYD-MEL-SYD around Australian Open time ... I got burned by this a few years ago as EVERY seat on QF was sold on some days (even J at AUD 1000+ for one-way was sold out). Book ahead if you know your dates. Only a few days sell out like this, but surprising when it does (SYD-MEL has more seats available than any city pair in US, very busy route).