You should be very happy that you are not banned. I've seen many people banned recently and I'm seriously scared right now. I don't know how many posts I can write without being assaulted by banning team.
Afaik, there isn't a certain number of posts that you need to accumulate in order for you to get banned. The main point for you to get banned by posting is posting nonsense post (usually bump, +1, single pictures etc.) and replies that are really far from what the topic really is. You can actually post as many as you want and as you like, as long as it is constructive and doesn't stray away from what is being tackled upon in the topic.
Have you read the forum guidelines?
Although the staff seems to miss some of the "good spammers".
That's what I have stated in my previous comment. Not sure if you read that one entirely or understood it clearly. The users who post useless and off-topic replies are more likely to get a ban than those who posts more often but do not post insubstantial ones. Well it is clearly stated in the forum guidelines, and one user (or staff, can't clearly remember who) stated that anyone without the signature ad in their signature space is fine to engage in different topics and may reply off-topic posts as well, as their intentions are somewhat related to join the discussion. Whereas, those who wear signature banners and spams or posts insubstantial replies/posts are more likely to get a ban because it is a way to boost their post count.