As is often the case, my goals for producing prints often exceed the time available. I have on several occasions prepared more sheets of paper with cyanotype chemicals and had them go to waste unprinted. When not used, they seem to go from yellow to green overnight and don't produce consistent results when that happens.
Last night, I coated 2 8x10's and 2 4x5 papers and didn't get a chance to use the 4x5's. So I put them in a black plastic bag in the freezer overnight (with the film I hoard). I took them out of the freezer this evening, gave them a few minutes to warm up to room temp, and put them to use in the contact printing frame. They looked bright yellow just like when they went in to the freezer. They printed just fine and are in the wash now. Nice and dark and consistent like I'd expect out of a freshly coated cyanotype.
I have no idea how long it would be good in the freezer before it deteriorates. Even in a worse case of a day or two, it would still save lots of time and let me use shorter blocks of time over the coarse of a weekend to produce some nice prints.