Question about stored breastmilk

My son is 6 weeks old, and for the first 10 days, he was in the NICU. He had blood sugar issues, so they closely monitored his input and output. The NICU started with him drinking an ounce of pumped milk and then spending time at the breast, and then moved to breastfeeding first... Followed by a bottle of pumped milk. I pumped for 15 minutes (double electric) after each feeding. They told me when we left, to continue that routine until he was satisfied at the breast and no longer wanted the bottle of pumped milk. It took a few weeks, but he is EBF on demand now. There are still times that I have to pump during the mornings and late in the evening, but lately, I've been having to throw away refrigerated milk because even though I freeze the milk I pump, I like to keep one bottle in the fridge. My question is... If you have breastmilk in the fridge for a few days, and it looks like it's not going to be used, can you freeze it? Or once it's in the fridge, do you need to throw it away? I was thinking of putting my first pump in the mornings in the fridge, and freezing it the next morning and replacing it with the new pump each morning, but I don't know if that's a no no.