Assuming you will be starting the trip from Australia, you could consider joining AAdvantage and undertaking their Platinum Challenge. Depending on the airfare paid, you could attain AA Platinum status by the time you reach LA.
Since you say you have an 8 hour layover, I assume this pard of a connection on the return journey to Australia since the LAX-Australia flights depart late at night (except QF8). So with AAdvantage Platinum status (OneWorld Sapphire) you can get access to the AA Lounge at T4 when departing on an international flight, or to the QF lounges at TBI if departing from that terminal.
What you don't get with AAdvantage Platinum status is access to AA's Admirals Club lounges when flying with AA domestically, except if you have a same-day international connection on a OneWorld airline.