Some forum communities hate it when someone revives old threads and much prefer new threads on the same topics. Others have the opposite preference. As far as I know, Tapas has never expressed a preference, but personally I would agree with you that a fewer long threads are preferable.
When a person self-promotes to ten or so threads in a row, I do find that pointless. The behavior wss discussed in the lounge board at one point iirc. I have sent direct messages to creators before when I see this happen. They seem to calm down after that, but that is a very individual solution which involves dealing with every individual. I suspect that these creators are have very recently joined and are posting for the first time out they haven't been to the forums in months before doing this. I see no good way of curving the behavior before it occurs since they aren't here beforehand to see any warnings against it.