My GF kept her crock pot on at night with water in it. You could also just place a small amount of water on the stove to boil, (before you go to bed) and make your formula with a small portion of boiling water and the rest just room temperature water. A small bit of water in a pot will boil in 2 minutes, then mix with room temp water. Maybe an ounce of boiling water to 5 ounces of room temp....you'd have to play with that during the day with just plain water to get the ratio right. So much faster than placing the whole bottle into the hot water, kwim?