Dear Lakewhut,
The Jewish milk companies have a much later date on the bottle. They compete over who can push the dates further. Because most Jewish stores carry several different companies. So every bottle sold to the consumer is an advantage over the competitor. Whereas in the non-Jewish stores, they generally carry one brand of milk and maybe one generic label. So it matters if the store carries your brand or not. It matters how well it lasts. Not the dates on the bottle.
OU-D and Star-D milk, generally go at least a week past the date. But Cholev Yisroel will barely get there. But it is the same milk. The dates are different. And maybe sometimes your local store may have bad refrigeration and the like.