Stored breastmilk question

Cindy • 25 yo. FTM to a Baby girl. Grace Elena<3
I am pumping my Breast milk. I know it's good in the fridge for up to a week , but what about once I take the milk out of the fridge and heat it up? How long does it last then? Is there a difference to whether I leave it standing at room temperature vs heating it up after it's been in the fridge?