I did the Oodnadatta track last month. Road conditions were fair to very good. The northern section was corrugated, but ok. It was being graded into William Creek as we drove through and smooth as a baby's bum. The southern sections were good. I could have sat on 80k easily for most of it, I wasn't towing. We spent 5 days traveling it and pretty much stopped in and had a look at most of the "attractions". Cattle can be a worry, we saw a few on the northern section.
SWMBO's father was towing his Kokoda Off Road van with his 100 Series TD & sat on 60 to 75 most of it.
This is the northern section, Marla to Oodnadatta in 10 minutes. Its at 16x speed....
https://www.youtube.com/watch?v=ZQG-TqP9DPYWe saw some funny things on the way through...and have some funny pictures...
A Volvo XC60, all by its self on the side of the track with the space saver on it, flat as a pancake...The original tyre was at William Creek with a couple of nice holes through the side wall.
An old Jayco Wind Up Camper on the Halligan Bay Road with a broken Stub Axle. From memory it took about 5 days for the flat bed to come and get them.
But that's all changed now with the rain over the last few days.
I have driven the Bourke to Wanaaring Road on numerous occasions. The worst was about 5 years ago after summer rains and before it had been graded. An absolute shocker, some of the worst ruts and corrugations i have ever had the pleasure of driving on. If you're lucky to catch it after its been graded, its smooth sailing....
So as you said, I suppose it really depends on road conditions, what you want to stop and look at, how much time you have. But i would calculate your time on say 60klm and work it from there.