All COs have to work their allocation of cases in rotation. They take the first, do everything they can for the time (sending out queries, or ticking off replies), then put that to the back and take the next, then the next, then the next, and so on. They don't take any file out of order. Any replies go to your file wherever it is in the queue, and the CO won't see them until it's your file's turn to be looked at again. The COs' job is to focus on moving their cases through, so telling people 'now your case is doing this, now your case is doing that' is not part of it, as that time could be better spent doing something on another person's application which would get it one step nearer to granting their visa. This is why EVERYONE spends long periods of time with no contact from INZ. These times are when the CO doesn't need any more information, and hasn't any news of a result to give.