You do not need to use boiled water for preparing formula as long as your baby is healthy. It's not what we'd generally recommend, but, if it gives you satisfaction, or you want to reassure yourself that the water is completely safe, then go for it (just remember this is a little harder to do on a plane). If you do boil the water, first make sure the water has reached a rolling boil for at least 1 minute, otherwise, you're not killing any germs and just wasting everyone's time. Next, remember to let the water cool completely before using it to make up your bottle, in order to eliminate the chances of burning the baby. It will take at least 20 minutes for boiling water to cool to a drinkable temperature without assistance (i.e. running the hot bottle under a cold tap). Another reason to reconsider using boiling water for formula is that using such hot water for preparing the formula can break down some nutrients, making the formula, lessening the nutritional value of your baby's meal.