As I've matured these past couple years, I've noticed a great decline of my use of NG. I used to be a 10+ poster a day, join chat rooms (paltalk, etc), in order for fellow BBS users to appreciate me a bit more. Over time I guess I learned that trying to get respect from strangers is unnecessary, and fairly stupid. Now I really only post in threads that have a question that require a legitimate, intellectual answer or piece of advice.
But I guess to answer to your question... I guess I would say it would be good to have a balance between post style. If the situation is appropiate, and you're sure you won't get banned, its ok from time to time to post something silly, but don't abuse the thought.
On the other hand, don't feel like it's useless or not cool to provide an intelligent response, while some may flame you for it, and not conforming to the immature ways of many NG users, somebody out there really does appreciate the info you provide them.