I think it depends on what kind of stock and what you are going to do with it. I boil the crap out of most of my stock after refrigerating it overnight. I reduce it to a syrup which turns into a block of frigging rubber when I put it in the fridge. It lasts forever that way. That said, I do think there are consequences to using a rapid boil and also to reducing it that far. You change the flavor somewhat. I don't find it very noticeable in beef or veal stock but I think it is easily noticed in chicken stock. Where it does matter is if you intend to reconstitute the chicken stock to use in a very simple dish such as homemade chicken noodle soup. It's not going to taste bad at all but it will have lost some of that pure chicken and fresh aromatic goodness that makes a simple chicken soup so radically good. For sauces I don't think it matters at all and in fact personally think boiling the crap out of the stock improves it for sauces because you do seem to get some Maillard type reactions going on and it does seem to improve it in that way. For any kind of soup or dish where the chicken stock is just added for more of a foundation or background flavor, or where it is going to be cooked for a long time, I don't think it matters at all. If you were planning to use it for a very simple chicken soup or a similar type dish where the chicken stock alone is really most if not all of the flavor, then I wouldn't reduce it that far and I wouldn't boil it so vigorously to reduce. My personal experience has been that reducing it by a third or half is the most I would do for that purpose. Either that or when I reconstituted it, I would simmer it for an hour with some fresh aromatics and some ground chicken to get back what you lost or changed in flavor. Lastly, the only thing I am addressing is taste and not any cloudiness issues. Beyond washing or roasting the bones and skimming for the first hour, I don't care enough about any slight cloudiness to pay attention to it.