One way to keep track of your hives during the winter without openning them is to listen to them.
Put your ear to the side of the hive and listen to the hum. Listening to the hives you can determine where the cluster is located: bottom or top box, front or back, and which side.
This information along with how the hive was situated when you put them to bed for the winter, can help determine what actions, if any that you will need to take.
Good luck this winter.