Bumping question

I cant seem to find an answer to this so i'll ask here. I often see threads bumped more than once in 48 hours by the thread owner. No one has replied after the last bump. How is that possible? I thought there is a limit?

 

There is only a limit from when you first create the thread. Until someone responds, you must wait 2 days. This limit is gone after the first post has been made.

 

Thanks!