How long will you stay in the shop? If you stay for around 8 hours, you may buy a fridge to go to store your milk. It could stay cold for around 8 hours. For breast milk under room temperature, it could stay for around 6 hours. So, you have total of 14 hours to keep the milk. Once you arrive home, put it into the refrigerator so that it could be kept a bit longer. But you must let bb drink it soonest possible.