Frozen Breastmilk

Hello Doctor,

To prepare for back to work, I started freezing some breastmilk about 3 months ago. I read that that wasn't necessary and that the breastmilk supplied to your infant should be closer aligned to their age and nutritional needs. I'm confused. Also, what is the time frame for refrigerated (not frozen) breastmilk? Any guidance with this would be great.