QF8 usually has the lightest load of any of the trans-pacific flights. However there are weeks when QF has every single flight oversold and it will be 100% full for days at a time (even with pax missing connections, etc. -- there are enough standbys to fill the plane). With the 744ERs it can operate with all seats filled even when headwinds are especially strong. Only the MEL flight is sometimes weight-limited to the point of leaving some seats empty (but then MEL is not often sold out). Avoiding SYD is probably the most effective strategy to find some empty seats.