How long is heated breast milk good for?

Abbie
So I pumped this morning, it's been in the fridge all day. I just fed my LO from the boobs and heated an oz in a bottle. She only took half an ounce so she still has another ounce. How long is it good for? I want to use it for my next feeding in probably 2 or 3 hours or so. Can I leave it out or should I refrigerate it?