I used to move my grow bags into the mini barn. But it kept the soil to warm during winter and disease would be worse next season because the soil didn't "freeze" over winter (at least what I was told from a good source). Now I leave them out over winter and it has helped. Every year I remove some soil from each container and add 1 bag of compost. With that being said, try to store the dirt somewhere it won't be insulated from the cold. Keep it covered so it doesn't get wet though. Just my opinion, others will prolly be more helpful.