DD started sucking her thumb at 6 months and now at 13 months does it constantly. She always does it to get to sleep, to calm herself if upset but also will just do it while watching TV or listening to a story. I've heard it's not great for their teeth but does it matter with milk teeth? And has anyone had experience of this and their kid grew out of it at a young age? Can you encourage them to stop? Or does it not really matter? Don't want to make an issue of it if she might stop of her own accord in a few months.