Thanks for your thoughts, WalrusWilram, very good points! Yes, I think it's very easy to get discouraged initially when things seem to be dying down, and you do generate more energy and interest for a title when you put effort into keeping it going. You gave good examples and I like your suggestions to tweak thumbnails, cover images, and titles.
One thing I'd like to add is trying a rotation on social media channels. You have to do this anyway on reddit, since many subreddits have strict posting policies when it comes to self-advertising. But get in the habit of putting up new ads in different places. One thing I'm trying to do is create some new ads in photoshop for banner ads, and then rotate those out every few weeks.