Even with receiving the occasional sMerit, this is just an estimate, I'm fairly certain I won't see my next forum rank for about three years. I'm uncertain if that is the intended result.
Do not loose hope. We can see changes to this merit system as well in future. Thyemos has mentioned it one of the comments. He also said that if merit system fails to control the spam on the forum, he will be forced to take more harsh decisions like completely removing signature campaigns. Ranks will become meaningless for most of the members then.