To your original question, the timing would be for one breast plus a little to account for the additional thermal mass in the smoker. IE: if you were going by time alone you'd give it 3.5 hours plus maybe a half hour for the rebound time of putting 14lbs of cold meat in your smoker. It'll likely take at least a half hour to get back up to 225˚. So, in this scenario, you're right on the money with your estimate of 4 hours.
However.....
Turkey in my opinion does a LOT better at higher temps. I run mine at 325+. At those temps I get a 12-14 pound bird done in 4 hours. I do use more smoke wood or a stronger wood like hickory to make up for the shorter ride, but my birds always have plenty of smoke. And tender skin. and moist meat.
I just prefer the texture of a bird smoked at higher temperature. I've done low and slow and feel the meat gets a grainy, almost mushy texture, and the moisture seems to be more infused in the finished product. While a hot and fast bird is more "meaty" and the moisture seems to be between the fibers, allowing it to flow more freely out of the meat into my mouth. :) I know what you're thinking, that the hot and fast method is more likely to dry it out, but this hasn't been a problem, not yet anyway.
Anyway, no matter what you do, get the meat to a safe temperature. If you don't have a probe thermometer go to the store and get one. You can get the bi-metal ones with a dial for just a few bucks. Then you just calibrate it in either boiling water or an ice bath and you're good to go.