According to Macworld, the Apple Magic Mouse 2's built-in Li-ion battery should be good for a month's use. It & the Magic Keyboard 2 are both fast-charging devices, the mouse can get enough charge for 9 hours of use from a 2-minute charge. So the fact that they automatically disconnect from Bluetooth when charging is not really a problem. Just plug one in & take a short break, you probably need it. Come back a few minutes later & unplug, it will re-pair with Bluetooth without intervention.