I don't know as the milk will 'go bad' per se, but then I can't say that I've ever checked. Generally speaking, you've got about a week before she dries up to the point that the milk won't come back. This can vary depending on how heavy of a milker she is, too. If we lost a calf and wanted to put another calf on that cow, we tried to do it within the first 3 or 4 days. Hope this helps.
