I don't have an exact answer for you, but a lot of it depends on how fresh they are when you get them. They may have been in the supplier's or pet store's freezer for quite some time. I've fed a few that had that "freezer" smell to them and my snake was reluctant to eat them. I had just bought them, but they must have been frozen for a long time before that. If you're up to it, you could buy live and kill them yourself and freeze them in air tight containers or bags, maybe a couple of weeks in advance.
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