Soups: Can I leave bones in indefinitely?
I always leave bones in stews and stocks, even when freezing. I don't think there is anything in bones that would accelerate spoilage, specially after being cooked for so long in high temperatures. 

Nutritionally, I think there are two factors to consider


Bones are composed by a matrix of proteins and minerals. Cooking denaturate some of the protein tissues adding flavour and nutritional value (amino acids) to the broth. The longer you cook, the more you extract, until reaching a threshold. Hervé This has interesting experiments where he weights a piece of meat after different times of cooking and measure the 'flavour' it delivers by seeing how much weights it lost over cooking time. His conclusion is that cooking over this threshold is worthless. The same is true for vegetables, and probably for bones, each with a different threshold.
What make bones hard is the mineral matrix, composed by calcium among others. The reaction between acetic acid (present in the vinegar) and the calcium produce calcium acetate which is soluble in the stock, weakening the bones and making them softer. Maybe someone can add on that, but I am not aware of the nutritional value of sodium acetate. 


So I would bet that leaving the bones in the stew can be at most beneficial. If you have cooked enough, it will probably not make much difference. If you have not cooked enough, the process of reheating with the bones will bring additional flavour and nutrition.