For AC passengers just 30 minutes are enough since most of the AC PASSENGERS are booked E TICKET.So IR, the AC Booking may be advanced to 9.30 am to 10.00 am and block the Agents from 9.30 am TO 9.45 am and the regular non AC sleeper class /Sitting as usual 10.00 am to 11 am with blocking of Agents Booking from 10.00 am to 10.30 am..