If I remember correctly, in her book Herman does emphasize that the three-stage process is not linear. That is, people might move back and forth between different stages, depending on many different variables.

That's certainly been true for me, and when I revisit each 'phase' I come back to a different spot, one a little closer to some kind of end point. For example, after T and I established some kind of safety, I did some exposure therapy. That helped, so we could do some cognitive work on issues in the present, and then because I still had problems with the trauma memories, some more exposure. Then more present-day stuff. Now we are going back to the trauma story again. This has taken years! But it's a slow and steady progress.