Sometimes, I think that people won't post because they really LIKE a timeline, and have no particular criticisms, and just want to see some more. On the other hand, it could be that several other recent posts have covered the same time period and people are just sick of that particular historical time and place. It's actually very difficult to tell why people are interested in something or not, because none of us can read each others' minds. A lot of it is just luck of the draw, I think. A timeline posted one day might get a couple of interesting replies, which will stimulate more discussion, which will start a long thread. If it's posted the next day, no one might be interested at the time, or people's attention is focused on a couple of other posts, and the whole thing just withers and dies.
I think you just have to post what you find interesting, cross your fingers, and hope for the best!