Hello, my sis is a Virgin Blue pilot and I don't think the limits are true for domestic travel, only for international.
I would check the info on the airlines website, they usually have a bunch of info up online.
Who are you flying with?
All of them allow up to 5 litres of alcohol - so i'm sure they wouldnt mind up to 5 litres of breast milk! lol!
Also, info on travelling with infants/children in general:
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