Well, i have to say that i also been with three co. and looking for the next one.In some of them i have seen the most incompetent people trying to manage a plain with a serious lack of respect for the crew,for the pax. and even worse,education and culture.
We could talk 'bout "friendships" or simply years operating for the same co.which in the end leads us to non-prepared people for the position.
I personally would say that when you find somebody is mature and well prepared to represent a co. is the time of promoting.