Hi, I am just wondering how are you guys sterilizing the flask to keep the hot water in for fresh feeds? I have bought the fisher price one which is stainless inside and the bottle of milton sterilizing fluid says its it not for use on metal. Was just wondering if anyone had tried theirs in a steam sterilizer? If so did it get damaged or was it ok? I know the risk of bugs from something you use only for hot water is low but just want to be able to sterilize it before first use and maybe once a week or so? What do you think?