I agree with Emily. Think of how people feel after they work out, after they meditate. I believe there are two ways to look at the window of tolerance: the person's state (current functioning) and the person's trait (long-term functioning). As therapists work with their clients developing strategies to manage hyper-arousal and hypo-arousal, and learn more about the practices that can widen their window of tolerance (or resiliency), states can grow into traits. That is my thinking.
I appreciate this discussion! And I didn't know about the window or resilience, so thanks for that!