I don't usually use K blue for long cooks, but I know that including the lit, I'll heap up a whole 15 lb. bag of Stubbs briqs to last as long as I need for just about any cook, 225-250*, 14hr+.... unless the weather's really brutal.
I usually fill up the cooker with three-four butts, or one brisket and two butts...largest ones I can fit, smoking water in the pan, and it's a ECB (brinkman) charcoal pan that allows me to heap another layer or more briqs than the OE pan does.
As for chicken in the kettle, one heaping chimney will do it without adding any more in nice weather. I've done a couple of beercan chicken cooks with two in the middle of the two charcoal holders, half a chimney in each, and was able to pretty much keep temps 350-400 til the birds were done.
You probably need a few more briqs to keep temps that high if you put two or three fryers with legs pointed toward all the briqs on one side of the kettle, but I like that method better, actually.
In case you're wondering, ceramic cookers use very little in terms of fuel, and wsm's use a good bit more than kettles. K blue is so cheap though, it's not a big deal in the scheme of things. I got several bags from HD a couple of weeks ago on sale for about 28 cents per lb. if I remember correctly. I just wish the local Lowes would put the Stubbs on sale like they've done in other parts of the country.