3 posts minimum, that is the rule, yes. However, I did make a post a time ago saying that there are understandable exceptions to that rule, namely, in a situation where you're keeping the action moving (especially if we're waiting on you in order to move to the next block of the day) and it doesn't impede anybody else from participating. Use your best discretion, and if I think you're breaking that rule in an inappropriate manner, then I'll let you know.
~ Mark ~