I use rechargeable batteries and I typically leave the mouse switched on all of the time and let it sleep on its own when inactive. I have a number of devices with rechargeable AAAs so I always have some AAAs ready and fully charged. I have one Toshiba mouse on each of two computers that I use a lot. I would say that the rechargeable batteries go a couple of months per charge. I will keep closer track on my next battery changes to give you a more precise estimate.