15 degree weather won't hurt anything as long as you are careful handling the plastic case and give the electronics a few minutes to acclimate to the indoor temp and humidity. Cold electronics will crackle, but that's about it.

And BTW Fran, if you think this big build up of the E-60 is going to make me jealous, you're absolutely right. I'm waiting to hear from an interested party regarding the 3K. But if I sell, I'll be without an arranger because you obvioulsy are becoming very attached to that E-60.