Until C was 6mths I would only add the formula when it was needed to the bottles of boiled water. After 6mths I just made bottles up and left them in the fridge for that day/night. We kept our boiled water in a jug on the bench, tho the jug I used had a full seal - if it hadn't I probably would've kept it in the fridge.
When C was little I would take a couple of sterilised bottles, the formula dispenser (with a few formula sections filled) and a thermos of boiled water into the bedroom with me and left them by the bed. That way I didn't even need to leave the bed to bottle feed her in the night, I'd just quickly make up a bottle with water and formula in bed. The first feed would often be a little too warm so I'd just let it sit for a few minutes and the second feed was normally the perfect temp.
Can you tell I'm not a night person??