reusing unfinished bm bottle?

Meganequine

I've looked at kellymom and some other websites, and there is a lot of mixed information out there.  My LC said I didn't have to toss the unfinished portion of a bottle, but I can't remember how long she said it was good for.

If my LO leaves like 1-2 oz in his bottle I stick it back in the fridge and use it again with/in the next 24 hours for a feeding.  (He is only getting 1-2 bottles a day)  I hate to waste the milk!  Sometimes the milk was fresh and othertimes pulled from the fridge (pumped w/in the last 3 days).  My LO is sparatic in how much he eats, sometimes he only wants 2 oz and other times he's taken 6 oz, so it's hard to predict a bottle.  I make bottles with 3-4 oz and have 2 oz back up bottle if he wants more.

What do you ladies do with your left-over BM?  How would I know if it went "bad"?