I believe with frequend "Dumps" the bacteria do not have time to grow all that much.. And there are two types of bacteria Aerobic and anaerobic The first type can indeed live in your black tank (It means they like an oxygen rich (Air Supplied) enviorment) the second (no air) live under ground. Those are very very stinky. The only time I've had a noticable Stink issue is when I leave a dump valve open so the Anaerobic bacteria gasses back up the pipe.
But I flush often
IF I'm going to be more than 2 weeks w/o a dump.. I do have a chemical (Well Biological) I add.