Interesting point by sir KDM. I have in the past ack'd roster changes, for example because I'm on G's and my next trip is at dark o'clock on the first day back...and I want to know what's going on so I can plan my life! However, about 6 months ago I changed to a blanket self-ban on ack's when I realised that they're mostly just manipulating the roster in as many different ways as they can just to save the the odd 30mins HDP here and there. I guess being bored at 0400 up in CC that's what they do to fill up their time.