Having done a similar journey too, it'll do for me too.

Like Matt and Stewart I was in no rush, took 2 1/2 days to get to Brisbane and just under 2 to get back to Sydney.
Rides like that in the UK are nigh on impossible - it's not that big, you'd hit the sea... and decent weather helps... when it's anything less than warm and sunny, long distance riding can be hard work.