Can't remember for sure, but i'd say around 2 years. Maybe more. I'll think about joining that forum, but the reason i'm hestitant is that there's a limit to how much criticism i can take before becoming butthurt.
Indeed, criticism is what makes you improve, but encouragement is what motivates you. Most people will get demotivated sooner or later if they never receive a kind word about their works, so the optimal situation would be one part criticism and one part encouragement. :U