What is the expected timeframe one would expect to see paroxysmal sympathetic hyperactivity/sympathetic storming persist post-traumatic brain injury?

I've personally seen as long as 30+ days but usually less.

I agree with Dr. @Dr. First Last that most storming usually resolves in a month, oftentimes shorter. That being said, I have had patients who develop storming for months to years, requiring long-term assessment and treatment. This tends to be the most severe TBI patients.