Halving being nearby has nothing to do with the number of posts people make in a day. There might be a thread about it, but I don't think it's enough to keep the number of monthly and daily posts of all members increasing. 
 
The number of monthly posts reduced could be either because active members here have also reduced or because some people have also diverted their attention to Altcointalk as a result of Mixers being moved to that side. Some members might still be active here but might not be producing as many posts as they used to in the past since they are now posting on different forums.