This is interesting. Once you've paired a Pencil with the iPad Pro, the battery will simply just drain on the Pencil, even if you're not using the Pencil! The only way to turn the Pencil "off" is to turn off Bluetooth on the iPad Pro. The problem with this is that when you turn off Bluetooth, it effectively removes the Apple Pencil from the iPad which is why the Pencil then goes to "sleep." That means when you turn on Bluetooth again, you actually have to connect the Pencil to the Lightning port on the iPad Pro to get it to reinitialize the existing pairing, which is a bit of a nuisance. A bit peculiar, unless I'm missing something.