We are spending four weeks in Northern Europe over the summer with a couple of long days of driving. I intend on taking a flask of boiled water to sterilise the powder and making up the rest of the bottles with cooled boiled water. Is it ok to keep the boiled water at room temp I.e not in a cool bag when we are driving? We won't have any access to ice packs at the places we are staying so even if I put the bottles in a cool bag, they won't be chilled. I don't think the pre made bottles are feasible for the whole time as we are extremely tight on space already but we could probably take a couple to make it a bit easier. Thanks!