Being an organic has nothing to do with how long the milk will last. The real reason is the different process used to preserve it.
Regular milk undergoes pasteurization, the standard preservation process. It is usually heated to 145 degrees Fahrenheit to 160 degrees Fahrenheit. This kills bacteria, but not all. This has a shelf life of 15 to 17 days, if unopened and refrigerated.
In contrast, organic milk is treated at 280 degrees Celsius. This is called “ultra high temperature” processing or UHT. It kills everything, that is why organic milk lasts longer than regular milk.
Organic or other UHT treated milk lasts for 40 to 60 days.
There is also regular milk that has undergone UHT processing. One reason why they don’t produce all milk using UHT process is that it tastes different. The high temperature will caramelize some of the milk’s glucose and lactose.
* To help keep any milk fresh for as long as possible, store it in a fridge.