With the schedule back to 6 daily, the check-in desks are open all the time except for 0300-0500 (and even then there may be someone there who can do it). However, the check-in staff are contracted and sometimes all change shift/have food/gossip at the same time (e.g. around 1800 or 2200) or have staff meetings in the office which is not in the main part of the terminal. Their standard procedure is to have one or two staff at the desks or at the very far end if you are facing the security checkpoints where they do standby travel etc. during the times when most of the check-in staff are absent.