I had one box used for roosting one year. Not so much usually. But this one year was exceptionally cold and when I opened the box in the spring it had 2 to 3 inches of droppings in the bottom! (and a dead BB :( but it had clearly continued to be used after that ones death) so that was really cool. I never took a photo of the droppings but really wish I had now. It hasn’t happened since. Often have to clean out a small number of droppings in the spring, but nothing indicating REGULAR use except for that once.