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Jerzee, I store the sandwiches in an airtight container at room temperature. I've never had any issues with rancidity or any other negative effects, but I've never tried one that was more than two days old -- they just don't stick around that long.

I'm sure you could safely keep them for longer if you did store them in the fridge. If you do, however, I'd recommend bringing them to room temperature before consumption. There's nothing pleasant about cold buttercream, and any baked good has a better texture and flavor at room temperature than it does cold.

I've also had success with storing the cookie dough in the refrigerator for up to two days before baking. The cookies tend to spread a little less during baking, yielding slightly smaller results than fresh dough, but their texture and flavor are uneffected. Hope that helps.

Rachel, you're welcome! And thank YOU for such positive feedback. Good to hear from you. I hope all is well...

Batter, also very welcome. ;o)

oh my god thank you thank you thank you