Sterilising is a funny thing really. As I don't see that bottles can remain COMPLETELY sterile for very long. As soon as they come in to contact with air I'm sure some bugs jump onto them! I think boiling/steam is a good way to clean bottles though, but in the hospital that I work at we say use soapy, hot water and air dry on paper towels. Big change from years ago isn't it. Difficult for many parents to get their head around.