I do mine for between 4 and 6 hrs though I do confess to being paranoid about undercooked chicken! Put some screwed up balls of foil under it to lift it out of the fat that runs off. Eat with a spoon - it's yummy.
Just remembered what I did last time, put water in the cooker, about 2/3 the way up the bird, added garlic, peppercorns and bay leaves. Once cooked I kept the water to use as stock. Really nice, avoids the over cooked taste you get from re-boiling the carcass.