How long can I keep expressed breast milk out in the open for?

You can keep it at room temperature for up to 6 hours but advised to use or store it within 4 hours. If the breastmilk is especially warm, it's also advised to keep to four hours. If you put it at the back of your fridge, you can keep it for up to 5 days, although usage within 3 days is optimal. Back of deep freezer would be up to 12 months although usage within 6months is optimal. http://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/breast-milk-storage/art-20046350?pg=2