The warm / hot water for formula feeds should be made and used within 30 mins of the feed. Any left over water is to be discarded and fresh water is to be reheated. A few times, yes, while travelling, a flask is okay. But long term, always freshly heated / prepared water is best. Regarding the cleaning process, it seems alright currently. Make sure the brush is also cleaned routinely. The whole formula making process must be hygienic and sanitary, to prevent any infection formation. For any queries, kindly book an online consultation with me. You can check out my Instagram page @drbabymum for helpful tips ! Take care!