The problem with a series like Do Over is finding an ending. Since the premise of the story is the characters can go back in time, it is possible the story never ends. That is unfortunate for Dan since he develops stories with a wide range of characters and topics. Just look at his story site: time travel, dragons, politics, magic, religion, clones, dooms day. As much as I laughed and cried through the Do Over series, I am always happy to read a new chapter from Dan - regardless of the topic.
PS: if you haven't already, your next story should be The Beard...