I'm designing a device which uses Bluetooth 4.0 (Low Energy) and I noticed how hard it is to achieve decent battery life, but the average mouse or keyboard lasts months/years on two AA batteries. I know they are not using Bluetooth, but a custom RF protocol, but what is so fundamently different to BLE that the consumption is so low?
I believe that the wireless mice and keyboards only transmit when an event happens, while BLE has an ongoing "pairing" traffic. TX-on-demand moves the power consumption to the reciever (which is not on battery) but it makes it impossible to tell when the keyboard has gone out of range.
They're also single-direction (apart from keyboard LEDs, which may not be present), while BLE can exchange data in both directions.