Good question!
If we have the APU running and the YLO Elec Pump ON, the all is sweetness and light (hydraulically).
However, I assume you were wondering how long a windmilling engine will produce hydraulic power provided of course the Fire Pbs have not been activated.
On reducing IAS for a SE approach with one engine shutdown (Fire Pb not pressed) the PTU will begin to take over hydraulic duties around GD speed.
I’m sure others will chip in too with their experiences in the sim.
Cheers
mcdhu