Depends on the temp of the fridge - like if it is considered a 'deep freezer'. Freeze your milk flat so it'll store easier. Put the new frozen milk in the back so you know the milk in the front is what should be used first.
You can check this with La Leche League. :) Breast milk can be affected by freezing and get a slightly changed smell, but that does not mean it is spoiled.
3-6 months in freezer 6-12 months in feel freezer
It's 4 hours at room temperature, 24 hours in the fridge, 3 months in the freezer.
The ideal time frame it is good for would be 6 months. After that, it may start to lose some of its nutrients. Take care