FYI... I leave my BlueTooth on all the time, but use it rarely (lately not at all during a day), it amounts for 2% of my battery usage everyday. As of 4:30 today, 8h 47min on time, it amounts for 3m 53s of CPU time and 30m 10s awake time. Note that this is 2% of the 13% total usage, so in reality it is 0.26% of total battery drain in almost 9 hours well turned on but not used.
I will turn it off tomorrow and see how it does.