I seldom store ebm. First because my supply is insufficient, second I read somewhere saying bm nutrient/composition change from day to night and vary every months to accommodate baby needs for their growth. Maybe you can donate the very old ebm or make soap if they're still in good condition
These links may help you https://www.cdc.gov/breastfeeding/recommendations/handling_breastmilk.htm https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/breast-milk-storage/art-20046350
They say can up to 6 month in freezer just for bm. But i just kept for 3 month max just to be safe. Don't waste your frozen stash you can give your baby milk bath!