The problem is International - Domestic (or vice versa, albeit a bit less) to process all the formalities, turn baggage back in (sometimes you can, sometimes I have had to schlep it to domestic) and take the landside coach around the airport end (which will take longer if there is construction going on) etc.

Three hours is the minimum I would allot for this. (My usual connections have been SYD International to MEL, ADL, CNS, BNE or TSV.)