The studies assessing his method to date are small and with some inconsistent data. The 11-minute claim is largely anecdotal. We need to be cautious with applying proposed mechanisms (e.g., hormone responses to cold exposure) to systemic experiences. Our bodies are complex and influenced by many biological, psychological, and social inputs.
That's not to say you aren't experiencing a benefit. If it is good for your mood and you aren't experiencing side effects (I have not seen anything suggesting the dosages recommended by Hof are harmful), then I think it is worth continuing. Thank you for sharing your experience.