Not a question, just some info since the olds threads asking about it are locked. I was wondering if I should switch off paired sensors to save battery and according to the old threads for other watches it's not required.The watch isn't searching constantly, only when starting an activity that uses the sensor (e.g. external HR) or while you're in the sensors menu.
But I've also found another place where it connects to the external HR and that's when you go to the HR glance. You can test this by taking the watch off (although it should work when wearing the watch) and leaving it on a desk. Go to the HR glance and you'll see the connection alert and live HR. It doesn't happen while in the watch face view though.