I'd personally just store the milk in separate bags according to which day you pumped them, regardless of how many pumping sessions you had that day, but I wouldn't see the need to mix them until they're used? Also if your fridge isn't quite as cold as it should be then at least if any of the older milk goes a bit funny (you'll smell it!) then it won't ruin the whole lot - just my own opinion though.
Neither of mine ever took a bottle but went straight to a sippy cup around 6/7mo with no problems - does he already take water in one? DH warms the milk as that's what they're used to from bf. Also mine preferred softer spouts as I guess that's closer to the bf experience? But I'm sure a hard spout would be fine too if that's what you have. Actually when DD first took my milk from a cup, she really wasn't sure at all at first, until DH took the spout right off and she could kind of lap it from the open cup - once she realised what it was in there, she also realised she could actually get more milk (rather than spill it everywhere!) by using the spout.
Btw Sarah, there's no reason you'd remember me from 5 years ago but I was in a really dark place then and will always be so grateful for the help you gave me on here with DS's sleep during that notorious 3-4mo phase, so thanking you publicly
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Lovely to see your beautiful family growing
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