Often C”Y is not treated with the same care as C”A (or C”C – chalav companies).
When I lived “in town” the local kosher store would sometimes get a shipment of C”Y and it would be next to the fridge for a while (maybe an hour) until the worker put it in the fridge. It often did not last well after I bought it.
Now that I live OOT, the C”Y comes to a large, regular supermarket. When they get the C”Y they put it in the walk-in fridge and the milk stays good well past the due date.