[capt_noonie]

I usually do my cooking late at night. So once I'm done with everything, and I am ready to make stock for future meals, it's really late, like midnight. I put the crockpot on high (mine doesn't really get all that hot, no simmer even) and leave it until the next morning. Let it cool, and strain it from the crockpot to a smaller pot. Then I get yet another pot, and strain it again over a fine tea strainer. You could use cheese cloth too. I strain between pot 2 and 3 once or twice more, just in case. From here I put in fridge if I'm going to use it for the next days food, or if not, in the freezer.

Short answer: 6 to 8 hours.