i think 'international' is the key in the decision to decide whether to go to Plat or not. Another big benefit from being Plat is that you are higher up on the upgrade-with-points list and you can also call QF and request the release of award seats (eg in J) if none are available. You have to still do this a fair way ahead, but it does work.
So, if you have international travel planned, then really striving to get to Plat beforehand would be worthwhile (again, as long as you can do it reasonable economically). And then with that international travel, you could possible retain with the lower threshold.
For the international travel, if you do a "DONEX" [code for
D (discount J) class
ONE World RTW, with
X meaning the number of continents visited 3, 4 or 5 - the fare depends on the 3, 4 or 5. There are threads here on them.], then there are real tricks for maximising SC earn. With the DONEX, you get 16 flight segments to be used within and between continents, going RTW. If you want to go from Nth America to Europe, the straightforward way would be to fly (say) NYC-LHR. Noooo! You fly from LAX to an easterly point in Europe, say Doha (counted as Europe) and then another flight DOH-LHR. You might earn
twice the SCs as the most straightforward routing. This works because with a DONEX, you pay the same for up to 16 segments no matter if they are short or long. So always take the longest you can do. Also, different airlines within OneWorld earn differently for Qantas. An American Airlines flight will earn more on the same route than Qatar Airways, for instance. QF code share on American will earn more than same flight on an AA coded flight.
On this trip, I did a DONE4 RTW and the mileage (and SCs earned) I accumulated was actually twice RTW! 2,000 SCs for the one trip, including SYD-LAX-JFK and SIN-MEL in J on DSCs