How long should I leave my broody on her eggs?

[pelicanchook]

I've never had a broody before, and let her sit on 5 eggs since she seemed determined to next despite all my efforts to discourage her. The first egg hatched on day 21, and it is now day 24 and nothing else has hatched, and she is determined to stay sitting on them. I'm in Australia, and so there is no problem with cold termperatures - in fact she has resolutely sat on those eggs in days of 40-42C.
At what point should I take those eggs away from her and leave her to get on with raising one little chick?

 

[Ridgerunner]

That’s rough. If the eggs have not pipped, I’d do the hatching egg float test. Put them in a still basin of water and watch them. If anything is alive in them they will rock on their own pretty quickly. If they rock, put them back under the hen. But to be honest, if it is 24 days I would not have much hope.