The same is true with me. My time spent in forums also varies. It depends on my availability. As long as I finish posting my fifty limited post then I would stop.Mine usually varies from one hour to almost ten hours. If I see users who are online and are posting than I stay to make sure I do answer any questions they may have. Or sometimes I stay on my forum for creating new posts and with that I don't realise the time I spent on my forum.