I know we work on 6 mins for day time crew and 4 mins for night time crew, only for the fact that at night we have more people than you can poke a stick at, so its not worth recruiting people further away if they can only respond at night. During the day, as is the case everywhere, we would rather take 6 mins to get out than not at all, so we open the recruitment area a bit wider. Seems to work for us, as we have the books full at the moment.