Oregonbeek,
Can't remember where I saw it, but in Ontario Canada some overwinter in one deep. I think if you have 2 deeps you should be fine. If you're not sure, as insurance, this late fall, put some newspaper on the top of the frames in the top box, put another empty box on top and pour a 10 lb. bag of sugar in there, then put the lid on. That will provide stores for the bees to get in the winter.
Some one on this site used to do that, I think they were in New York.
Pugs