How long can you freeze plain cake layers (no icing) and still have them be usable? I have a lot of buttermilk leftover and was thinking about baking a bunch of chocolate cake layers to store in the freezer for when I need them.

Depends on how well they're wrapped but they should be good for three months if wrapped in Saran then aluminum foil.

I had some leftover layers from Christmas 2010. They were wrapped in plastic (Saran type) as well as heavy duty aluminum foil. I actually forgot they were in the freezer until I was ready to 'clean' out the old stuff. Curious if the layers were still good and how they would taste I decided to do a test. I thawed the layers then filled and frosted. To my surprise, the cake tasted like I had just made it...still moist and no freezer taste. I didn't tell family members it had been in the freezer for six months when they were devouring it. Afterwards I clued them in and the said...you're kidding! True story!