Most likely if you stay with any company for a long period of time you are going to wind up changing affiliate managers. With azoogle I've had 3 or 4 over the last 4 or so years... There are lots of things that can cause it too.... AM quitting, getting promoted, etc....
I wouldn't worry about it too much, unless of course your AM was giving you ideas the equivelant of printing money.. just suck it up and move on.. chances are your next affiliate manager may have different ideas and it might be what you need to take your shit to the next level.