Storing Breastmilk

Here is the link you need for all of your questions.

http://www.kellymom.com/bf/pumping/milkstorage.html

I don't think that you should have a problem topping off the bottle. when i breast fed, i would also pump some and store. i put it in little plastic playtex baggies with a twist tie. then i would get 2 or 3 baggies out and thaw, and feed. we would heat a bowl with water in the microwave, and place the baggies in the water to thaw on the kitchen counter. it usually didn't take long but you have to anticipate a little more if you want the baby to have warm milk. the milk should be good thawed for a couple of hours, like in a diaper bag, but not more than 2 or 3 I would suspect. you will definatley tell bad spoiled milk, it smells just like bad cows milk and the baby will not take it! YUCK!
I didn't use the playtex bottle system with the baggies. I just used the baggies to store the milk in the freezer. they were sterile and good sizes. you can't heat breast milk in the microwave it kills all the antibodies.
you can also contact the leche league and they should be able to help and answer some more questions.
good luck,
L.

la leche league is also an excellent resource for questions like this. I actually had this question and spoke with my lactation consultant and looked on the LLL site. Both said not to do it for the very reason you said. The temperatures are different, and your milk always tastes different depending on what you've eaten. I can't remember exactly what all they said, but you can check.

I think once you thaw it out, you can keep it cold for 24 hours, but that may be something else I don't remember. Google La Leche League.