The OWE fare is further limited to 20 segments total. So the segment limits stop you quite effectively from accumulating unlimited SCs (each segment gets one SC amount, based on mileage from origin to destination). The classic ways to maximize SCs on OWE in US are the seasonal ANC service (june through september) and SJU-LAX. SFO-BOS was good in the old QFF plan as it was 2701 miles (with 2700 miles being the threshold) -- less important after the May 25 QFF changes. In any case it is trivial to make QF Platinum on a DONE4 fare (which is the minimum you can buy from Australia). Just remember your OWE ends when you return to your city of origin.