HI,
You can saftly leave breastmilk in your refrigerators freezer for about 6 months and a deep freezer for a year.
You should NEVER freeze thawed or partially thawed breastmilk!!!!!!!!!!!! When you want to use frozen breastmilk make sure that you either put it in the fridge first or thaw under some hot water on the tap or a steam warmer never in boiled water it takes out all of the important nutirents!!!!!!!
So,here's the break up:
Refridgerated breastmilk=5-7 days
Frozen breastmilk=around 6 months(barring that its your refridgerator's freezer)
Thawed breastmilk=needs to be used with 24 hours
Frozen breastmilk(deep freeze)=around 12 months
I hope this helps!