I use the Lansinoh ones. Have never had a leak and they do freeze flat as long as you are careful to lay them flat in the freezer. I have never had to cut one open and get the milk from the bag into the bottle so I can't speak to ease of use in that regard (though no one at her daycare has complained about them). I have also used the Medela bags and they do not lay flat and the plastic was much thicker and harder.
i used lansinoh with DS and will probably this time around too. I reserved a special spot in my freezer to lay them flat (just half a square foot or so, or on top of a frozen pizza...whatever works Then I used a little plastic basket from target (one the size of a shoe box) and organized them with newest milk in back and oldest milk in front so it got used first. Since they froze flat, they were easy to "file" that way. They never leaked unless I dropped the frozen milk in the bag getting it out of the freezer...and then it would leak in the fridge as it was thawing. That was my fault, not the bag's I highly recommend these bags!
I highly recommend Lansinoh as well. I have used them, exclusively, my last 2 years of BFing. I've had a huge supply (would fill 2+ bags at every pump session excess for what either LO needed) I have only had a handful of them leak. I also thaw in a little dish just in case. It is quite easy to pour from once thawed. Yes, they freeze flat if you lay it that way in the freezer. Once frozen, I would also "file" them with the oldest in front/newest in back. That way rotation is easiest. I also have mine dated and numbered so that I can be sure I'm using the oldest first. With such a large stash, this was easiest for me.
I also use Lansinoh. Haven't had to thaw any yet, but they store easily and neatly. I put mine into a gallon ziploc and date the ziploc with the dates on the milk bags. I figure in a week span, which is about how many of the lansinoh bags I can fit in a gallon bag, it won't matter which date I use as long as I am using the larger bags in order.
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Another recommendation for the Lansinoh bags. I can lay them flat in my freezer and it seems like it's holding the milk. I haven't thawed milk from it yet, but I did have to pour milk out of it into a bottle. They don't have good spouts, so I poured the milk into my py.rex measuring cup that has a spout to pour into the bottles... I didn't want to spill.
Re: Recommend your milk storage bag, please!
I use the Lansinoh ones. Have never had a leak and they do freeze flat as long as you are careful to lay them flat in the freezer. I have never had to cut one open and get the milk from the bag into the bottle so I can't speak to ease of use in that regard (though no one at her daycare has complained about them). I have also used the Medela bags and they do not lay flat and the plastic was much thicker and harder.