I believe since bluetooth 3.0 (the 4S and 5 have 4.0) is so efficient and is dormant when not in use, that is not worth toggling on/off. Perhaps not even wifi. At least not along the same lines that GPS, LTE, or 3G drain battery life.
The new iPod Nano has bluetooth. Haven't read up much on it since it just came out, but if it gets days of battery life that should be a good indicator bluetooth on the iPhone doesn't cause battery loss.