How much breastmilk to store per bag for freezer stash?

Hi mummies, my LO is currently 2 months old and is fully breastfed. I have oversupply and have so far been storing around 140ml per bag for use. Any mummies can share their experience with how much recommended for storage per bag? What happens when you only need portion of it when u need to use, do you thaw in fridge and use within a day?