Just long enough that the feathers straightened. Sometimes I will assist by smooting the quills between my fingers.

Do not use a PAN of water, use a TEA KETTLE with the spout cap removed. With the kettle, the steam is pressurized and the pressure helps straighten the feathers. If you use a pan, the steam is to passive and tends to drench the feathers before they can revive.

Once the fletch is revived, gently blow the fletch to cool the fletch.