I have set the delay on ours to 45mins, that way if they only switch the AC off if no movement has been detected after 45mins, seems to work on mine or perhaps I'm a restless sleeper..
also worth checking .. does the area covered by the motion sensor include the bed? I have seen some fitted directly above the aircon unit and the motion detector picks up people walking around the bed but can't 'see' the bed..
Also some AC units beep when they receive an off signal, it may be possible to turn the beep off?