Hi,

The hospital told me I could keep breastmilk stored for 48hours in the fridge and once it's out of the fridge it keeps for 4 hours. You can freeze breastmilk as well - keeps for anything from 1 month to 6 months (just depends on what freezer compartment you have).

We were in hospital and I had to express milk for a while so I've got a nice stash of it waiting, how old are your little ones when you're starting to give a bottle?

I used formula i'll tell you anyway. I would boil the kettle, leave it to cool for 30 minutes then make up 6 bottles (with powder) - I know not everyone likes doing it, but you can all do it your own way. :P and store then for no more than 24 hours - although 6 was 24 hours worth, so no problems there.
We would wash the dirty bottles as needed and store them in the steriliser, then run it when it was full then the process would start again.
I wouldn't leave the breast milk longer than 24 hours either, but I don't know from personal experience sorry.