There are sooo many "don't do this" these days about EVERYTHING to do with babies and children.
I think as long as you are following the instructions on the formula tin you'll be fine. I can let you know what I do/have though.
I have at home bottles that don't leave the house. They are just plastic bottles that I wash and sterilize by boiling in a big pot (nipples, rings and bottle) I have an electric water kettle that I fill and boil twice then let cool. We make bottles as we need them so they are already room temp(sometimes a little warmer if the water is still cooling).
Then I have a playtex brand "disposable" 8-10oz bottle that's hangs out in my baby bag for on the go. They have the disposable liners that come sterilized so you just use and toss the liner no need to clean the bottle part. I carry extra nipples so I can use it up too 5 times a day without cleaning/sterilizing the nipples until I get home. Then in the bag I carry a thermus with sterilized water and a Tupperware container of the formula and a scoop. Again I make a bottle as I need it.
When we had our son you could make bottles up in advance but we have been told that is a no no now.
We are in the U.K. And have a perfect prep machine which is amazing!
When we are out I take a sterilised bottle and ready made formula. If she was due a feed in the next half hour I'd made a bottle up before we left home. But she doesn't have a routine as such other than she feeds in the day every two hours roughly so I can't always tell!
I'm not sure about now but with my DS I had those insulated bottle bags and if going anywhere during the day/for night feeds I'd keep the boiled water in the bottle inside those bags and then take a tub filled with enough formula for each feed with me. Come feeding time I'd take the bottle out, add the forumla and voila!
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