I turn it off every weekday for the commute to the office, then turn it back on while at the office, then off again for the commute home, then on for doing stuff with my Mac at home. Also for when I just checked to see if I have the original batteries in it since I bought it. Mouse preferences shows battery level at 56%, and I bought the mouse about two weeks after it was released (didn't have them in my Apple store on the day of release.)
I turn it off because I've found that bluetooth mice will wake up my Macbook while in the bag during transport, so it's mouse/keyboard off, disconnect everything, close lid, put in bag. Drive down interstate. Arrive at office. Open lid, enter password on wake, turn on mouse/keyboard, connect everything I'd connect (which is only power at the office.)