There are thresholds set up by post number - I use them on my board and the others that I am involved with use them as well. It's fun to get creative with the captions!! :thumbsup:
The caption changes as your post count does. At first they change more often, and then later, as your post count is higher, the caption changes less frequently. Personally, I enjoy the changing of the captions every 100-200 posts. Mine didn't change here for like 1,000 posts this last time. lol