my dd hasn't done that yet, but i also haven't offered her too much freezer milk
yet. anyways, my LC said you'll definitely know when it's no longer good, and your baby will refuse it. she also said some people's milk get a kind of soapy smell to it after a little while. again, it's safe for baby, just a question if he or she will take it. i haven't been brave enough to taste my milk, so i can't say if i experience the same thing.