Thanks very much guys. As long as OLCI works, I believe I shall be able to catch the 6pm flight easy even if I landed around 5pm (which is 40 minutes late).
I have checked LA800 ontime performance for the last week and none of it arrived later than 4:30. If LA800 was really delayed before departure, I guess I might even drop the whole trip, I have guested my wife into QF F and had good breakfast with her. It wasn't really for mileage run, so it doesn't matter