Fat oxidation/rancidity slows down with lower temps, but it won't stop, so freezing can't entirely prevent the development of rancidity (DOS), but it will slow DOS down.
If I made a recipe high in oils with a short shelf life (pumpkin seed oil, anyone?) and I wanted to keep the soap nice for as long as possible, I'd pop the soap in the freezer right after cure -- I wouldn't wait for any DOS to show up.
If you're talking about a few spots of DOS that sometimes appear in a normal soap... Honestly I don't see a lot of spread in the size or number of DOS freckles I sometimes see on my (pre EDTA) soaps. In fact, I've watched some DOS spots develop then fade as time goes on. I guess I don't get too concerned about this kind of DOS -- I just use the freckled bars first.
If you're talking about soap with overall DOS, as in most or all of the bar is turning a tell-tale orange-yellow... Hmmmm, not sure I'd bother with freezing. Of the one batch (early on in my soaping misadventures!) that did this, the soap had a funky odor as well as an unappealing look. It was not worth the trouble to freeze the bars -- they were already too far gone for me to want to use at all. I still have one in my "bone pile" for reference.
If the other soaps in my bone pile are any clue, they've proved to me that DOS does not spread from bar to bar like an infectious disease.
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