How long can milk be stored in the refrigerator after boiled and put in a Ball jar?
Unless you are using a canning method that is actually designed for long term storage and shelf stability, you cannot assume the food is sterilized or pasteurized by home processing methods.  

You should therefore not expect a refrigerated shelf life of more than 2-3 days, the same as if you had not processed it.

Finally, you are creating a low acid food with absolutely no protection (other than refrigeration) against botulism, so you definitely do not want to store it more than this guideline.

In addition to botulism which is not detectable by odor or taste, if you do see unusual appearance, especially bubbling, or detect an off odor or flavor, you should definitely discard.