Interestingly, I’ve spent time in all the places you mention. Keep in mind more people live in Southern California than all of Australia.
The places you mention are busy, and not really remote. I’d be willing to bet you can drive out of the most remote on your list to a gas station in well under 10 hours. Probably 5
Okay, sure the longest offroad stretches I've passed through before finding more fuel have been about ~160 miles. There are places in Baja, California, and Utah that have trails of about this length between closest fuel stations. If you're talking about just driving out after you've already driven in that cuts the effective length in half - so maybe ~8 hours at 10mph average.
A fun thing about Baja is that often these super remote fuel stations end up being closed or out of fuel, so you can't realistically do it without having the supplies and fuel for at least 2x what it looks like you should need.
That's basically where I'm getting my "two days" from- the time from one fuel station to the next with about ~8 hours of actual travel per day.
