Not that long. These were small thighs, refrigerated, I guess 5-10 minutes? Find some time that's long enough to cook the chicken and make stock, but not so long that the chicken gets tough. (I think I did mine for 10-12 minutes and I had a couple tough spots, but the water looked like a chicken broth.) Some folks would recommend removing the thighs after cooking the chicken, taking the meat off the bones, and then putting the bones back in to boil to enrich the stock. I just added a couple boullion cubes. ;)