Yeah after hours is definitely important... but I was pointing to when there is no after hours trading and that you can still exercise OTM or not exercise ITM if you so choose. So, downward drift is important when there is after hours trading... but if there is none, than a slight drift in say after hours ES futures... would not have a significant risk on whether someone is going to exercise or not. I would be more concerned with big moving news. When I was MM on European stocks, we would keep track of ADRs trading in the US and see if there was enough volume to hedge any OTM options that we could still exercise on the day of expiry... but volumes where too low for us and we hardly ever did anything. We did however sometimes opt to exercise OTM when suddenly news broke regarding some stock...