That depends on what you're taking if for. If you are asking how long is is safe to take it, I have not yet seen any toxicity studies showing any problems with long term use.
Without knowing both the initial temperature of the milk and the temperature of the environment it is in, I cannot do anything but give a meaningless guess. I can assume that milk freezes close...
The length of time it takes milk to spoil is variable and depends upon the initial quality of the milk, the bacterial load before and after pasteurization, packaging, handling and storage...