Hi Charli, i would put the later ebm in the fridge separately to let it chill and then mix it with the earlier ebm later in the day or night because every time you mix the fresh ebm with the chilled one, you're warming it up ever so slightly. That will not be good for hygiene and safety. If you mix all chilled ebm together, they are all done on the same day, like anna said, they can keep in the fridge for 3 days. HTH xx