I am going to be arriving from LAX into SYD, then transferring onto a domestic flight to Brisbane.

The problem is I arrive at 7:10am (QF310 - operated by AA) and my domestic flight isn't until 11:35am (QF560). That's four and a half hours. Granted, maybe only three hours after customs and transfers etc., but still a long time to wait.

What do people think is my best chance (without paying) for getting my flight to Brisbane changed to an earlier time?

Just ask at the counters once in the domestic terminal? Would it be a problem if my bags have already been checked on to Brisbane for the later flight?

Thanks for anyone's advice!