Yes Lone,
they can become susceptible again, but my stickies are around at most 2 weeks out of the hive, but once you kill the eggs off, they go back into hives and save the bees a bit of work. Some commercial guys store excess woodware in a coldroom after freezing, i guess it is how you want to proceed.
But phosphine is not acceptable if you wish to obtain organic certification.
cheers
Mark