So I know for freshly pumped milk roughly 8 to 10 hours it's still good. For refigerated 6 to 8. I've heard more for both but stick to less for safety sake. Two questions I can't seem to find a good answer for via my books and online skimming.

1) if I've taken milk from the fridge, warmed it, and not used it in 4 hours, can I put it back in the fridge and use it later than another 4 hours? Or does the 6-8 rule still apply?

2) for frozen milk, I've heard it's good to use after defrosted and warmed for up to 4 hours? I'm not sure I have that right though...

Any answers?