DD2 had to have colief and I couldn't do that so I started prepping bottles. I would do 2 at a time so I would always have one bottle. Made them with boiled water 10 mins after boiling, added colief, straight into the fridge. That way they were as sterile as I could make them. I never had any problems, but the bottles were never unused for more than about 4 hours, as dd2 fed little and often.
When taking out, I would take one from the fridge and then heat when out, or you could heat and keep warm. Again these would be premade. Although you could make one fresh because by the time you were out and about and needed it, your half hour would have passed and it would be ready to use.
Firstly as my little one isn't in a routine yet and is feeding on demand I can't time 30 mins before a feed to add the colief - in the instructions it says you can make up feeds in advance and add the colief before storing in the fridge but this goes against the advice not to make up and store feeds?!
Secondly it tells you to store colief in the fridge - how does this work when I go out and need to take the bottle of colief with me - or how can u take already made up feeds with the colief in out with you?!