I asked this once and was told by people who pollinate them that the window is very narrow. As soon as the spadix becomes unsheathed, it is ready to pollinate. Usually it will release the pollen at NIGHT. You have roughly 24 hours time, a little less. to brush the pollen down onto the female flower that you expose. After that, both the pollen and the flowers turn themselves off so to speak.
I do not think that you can 'save' alocasia pollen like we do Alocasia pollen (in a baggie in the refrigerator). It has a definite lifespan
