In your summation you totally ignore the fact that he had been clean & sober for 8 years. So yes, the fact that he had too much time on his hands and no way fill that time, played a major role in his sliding back into destructive patterns. His work and his self-sufficiency had been the key to his success over the addiction. Without that, his mind then wandered back towards his addiction. You can minimize that fact all you like, but you still remain wrong in doing so. Man is complex, and addictions are powerful. Far more succumb then continue in success when denied their coping outlets, because idle minds and hands are the devil's playground.
In your summation you totally ignore the fact that he had been clean & sober for 8 years.
There is way to prove that fact.
Therefore, we have no idea if he was sober for 8 years or 8 hours.