Storing, labeling, freezing, and organizing/storing milk has been a learning curve, for sure! Luckily, we have 2 freezers (no standalone freezer - just the freezer on our normal fridge, both in the kitchen and the one in the garage that we inherited from the prior owners of our house). Still, the frozen milk takes up the majority of the space in both freezers and has the tendency to avalanche when you open the freezer door!
Here is what works best for us:
1. Storing Fresh Milk in the Refrigerator
I usually keep 1-2 bottles' worth of milk in the refrigerator (to use when my in-laws babysit and on Sundays when C goes to the church nursery).
2. Storing and Labeling Milk in Freezer BagsIf I have more breastmilk than I need to keep fresh, I freeze it in breastmilk freezer bags. Refer to my post here on my brand recommendations on freezer bags! I use the "cone" (flange) piece of the pump as a funnel to pour the milk into the freezer bag - you don't want to get any milk in the seal of the bag or it can leak when you thaw it due to the milk expanding in the freezer. I freeze milk in consistent volumes - when C was a tiny baby, I started freezing in 4-ounce quantities (he started taking 4 ounces by 3 weeks old); since he was 4 months old until now, I've been freezing in 6-ounce quantities. Try to keep the volume of each bag consistent with how much you typically feed in a bottle - that way, you won't waste any when you thaw it, since you have to use milk within 24 hours after it's thawed. I use a Sharpie to label the freezer bag with the date it was expressed and the number of ounces. If I'm mixing milk that was expressed on different days, I use the OLDEST date. Milk is good in the freezer for 6 months (longer with a deep freezer), so it is important to know when it was expressed!
3. Freezing Milk Flat
4. Storing and Organizing Frozen Bags
After the freezer bags are frozen solid, I store them in gallon-size freezer Ziploc bags. This serves 2 purposes: one, it keeps the individual bags from avalanche-ing out on you when you open the freezer door, and two, it helps me to organize the milk by date so I can make sure to use the oldest milk first (first in, first out). I can typically fit 10 6-ounce bags of frozen milk into each Ziploc bag; I store one right-side up, and the next one upside down, in order to "file" them most efficiently. I then stick a post-it in the bag that has the date range of the milk in the bag, as well as the sequential order (#1, #2, etc.) This way, when I finish using the milk in Ziploc #1, I know I need to look for Ziploc #2. I use post-its instead of writing on the Ziploc itself because I re-use the Ziplocs (since they don't get dirty)...but I'm cheap like that. Write directly on the Ziplocs if it's easier for you :) Make sure to store frozen milk on the freezer shelves, NOT in the door - the temperature of items stored in the freezer door fluctuates much more than the items on the shelves, which is not good for breastmilk! You don't want it partially thawing and re-freezing over and over each time you open the freezer.
5. Thawing Frozen MilkWhen I need to use frozen milk, there are a few different ways I thaw it, depending on how much advance notice I have and how quickly I need the milk to thaw. The fastest way to thaw milk is to run the frozen bag under warm water until it thaws; this only takes a couple of minutes, and then you can pour the milk from the bag into a bottle (I use a small funnel for this). If I have 30 minutes to an hour before I need to use the milk, I'll just set the frozen bag on the counter and let it thaw at room temperature. Finally, if I don't need the milk until the next day, I thaw the milk in the refrigerator. This takes 12+ hours to fully thaw. If I need it slightly sooner than that (like 8-10 hours), I will put warm water in a Tupperware container, put the frozen bags in the warm water, and stick the Tupperware in the fridge. This helps the milk to thaw a little faster than it would just sitting in the fridge. Whatever you do, make sure to use the milk within 24 hours after it is fully thawed; after milk is frozen, it loses some of its anti-bacterial/anti-microbial properties, so it can grow bacteria faster than fresh milk (which is good at room temp for several hours).
6. Rotating the Freezer StashFrozen breastmilk is good in a regular freezer (the kind connected to your refrigerator) for 6 months; I think it's up to 12 months in a deep-freeze. So, you'll want to continuously rotate your freezer stash to maximize its "shelf life". Obviously, using a "first in, first out" method will help with this - labeling the bags helps you to always use the oldest milk first, rather than reaching for a bag at random. Also, I have a weekly "routine" to ensure my freezer stash stays current; since I work part-time, I have to pump at work every day to have milk to send to daycare.
On Mondays, I send previously-frozen milk; I take the appropriate number of bags out of the freezer on Sunday night and use the warm-water-in-a-Tupperware thawing method mentioned above to thaw the milk in the refrigerator overnight. On Monday mornings, I pour the thawed milk into bottles for C to drink at daycare during the day. Tuesdays through Fridays, I send fresh milk to daycare using the milk that I pumped at work the previous day. For instance, on Tuesday, C is drinking the milk that I pumped on Monday. I don't need any bottles on the weekends since I'm home to nurse, so on Fridays, I freeze all of the milk that I pump at work on Friday, as well as any excess milk from earlier in the week that may be sitting in my refrigerator.
Using this routine each week ensures that my freezer stash stays within its 6-month expiration, since I am using (older) frozen milk every Monday and freezing (newer) milk every Friday. This routine is important to keep milk from expiring in the freezer; the milk I pump on Friday would still be good to send to daycare on Monday, but I have to consistently use frozen milk and freeze new milk in order to keep the expiration current.