I've heard there is unofficial tehnique to leave A/T armed. When you press TO/GA (doesn't matter single/dual AP channel or AP off) A/T will engage GA mode.

On ILS approaches or when using IAN this can be flown, just don't let your speed to drop too much.

 

But mostly I fully disengage A/T.

disengage the entire autothrottle, not just speed mode

If you dissconnect the A/T via the throttle, the switch moves, powered by a solonoid, from the ARM position to OFF, so in case of a go arround, you would have to move it up to ARM again, however you can also manually set the desired thrust, can't you? At least you are the pilot. :wink:

My mistake, you're right, the switch drops to disarm. Having elected to land manually I suppose a manual GA is the preferred option.