This is a potential game changer for DH who is about to be a stay at home dad for the summer (teacher).
This morning baby drank 2 oz. fresh pumped room temp milk combined with 2 oz. refrigerated milk pumped yesterday. No problems! (I know you're only supposed to combine similar temperatures, but it was mixed immediately before consumption.)
SIL is going to try a defrosted 4 oz. straight from the fridge for his next feeding.
Yes, DD drank cold milk on a road trip (not straight out of the fridge, but from a cooler). The only reason I wouldn't do it all the time is because the fat sticks to the bottle when it's cold.
Also, I never worry about mixing different temperature milk. If I pump and I want to add the milk to another bottle in the fridge, I just dump it in warm. Never been a problem.