I have had the same question. I left my bats in my garage without any covers and I have been out of town for more than two months. It has been a pretty cold winter so far. What should I do to make sure they are not damage? Should I give them a light oiling?
you can give the bats a light sand and oil but
There's no need to oil unless the bats there are dry
As long as the garage is not damp the bats should be okay
Also it's okay to leave the the bats in the garage with the covers off as it allows the willow to breathe buy only leave them in there if the garage is dry.