All mice in the Pen Grip range include an automatic sleep function. Which will switch components off when they are left idle to preserve battery power. 

If your mouse is left on your desk overnight this system will work almost as well as switching your mouse off fully. So in this case it is not necessary to switch your mouse off, but doing so could still slightly extend your battery life.

However if you are traveling with your mouse and it is not switched off, the slight bumps that will occur in transit can wake the mouse up and over time drain the battery. So for the best possible battery performance while traveling we recommend setting the switch on the base of your mouse to OFF while it is not in use.