Fortunately, it is only proposed for Victoria but almost all of our country roads in Oz have a limit of 100 or 110kph.
The upside is time to enjoy the scenery and a fuel saving. The downside is extra accommodation costs on long trips.
Of course you can put in more hours on the bike but that is harder as you get older.
For me, around 500km (320 miles) is a comfortable/enjoyable day as most of my riding is on minor roads with slower bends and country towns to slow down for. Country town police are notoriously strict on those just passing through. There are several towns that I regularly go through in which I make sure that I am 5kph UNDER the limit just to be safe. Some of these towns, admittedly small but still on the highway, have limits of 50kph and some at 40kph. Third gear for a couple of km!
The longest that I have done is a bit over 800km (500 miles) and that took well over 10 hours with brief stops for fuel and food despite a short burst at 135kph for about 15 minutes (it can be done but you have to know where).
Macka