After sterelizing my bottles and my pump every 24h, I usually need to use them straight away so I've never used them dry. In fact when I came out of the hospital a month ago, I was told by an old auntie that right after sterelizing I should keep the bottles closed to avoid contamination. It is only a couple of days ago I read articles about how to dry up your bottles. Is it absolutely required? Is there any danger associated with not doing it? How do you dry your bottles and how long does it take you?