“Expiry” depends on how and where you store.
You can do both ways. Pump and freeze or pump and feed (fridge). What I did was pump into bottles > fridge > feed. Whatever excess I have in the fridge I will freeze at night. I always give my baby the freshest and newest milk in case she suddenly don’t wanna drink my milk (frozen stash) anymore.
Storage temperature and durations: https://kellymom.com/bf/pumpingmoms/milkstorage/milkstorage/?fbclid=IwAR2vy0e6o2wP9RCkCYs3GHdrOXsVYpz5FDnEE1eDGj_xi4Utko10JCfrcPA&mibextid=Zxz2cZ
After defrosting (do not refreeze if the ice particles inside is fully defrosted.), warm 2-3 mins depending on which warmer you are using. Can take out every 1 min to feel with your hands in case of overheating.
If milk is warmed and baby did not drink, use it within 2 hours.
If I’m doubt, just do a taste and smell test :) As long as it doesn’t taste sour, it should be good. For smell, if it smells like vomit, it may not necessarily be rancid, maybe just higher lipase in it (do a taste test to confirm.).
Iffah fafaa