Here are a few methods that I maintain in order to keep interest in my setting.

The first step I took when I started my setting three years ago was to establish a purpose for my world-building. I took inspiration from the work of Henry Darger, so I said from the beginning that my setting was intended to become a large scale opus. I have no short term goals for my setting.

The second step I took was to establish writing as a daily activity of mine. Before a day goes by, I take time to sit down to add content to my setting. I have no limit for how long I must write or how much content must be added. I just write daily.

The third step I took was to establish the limitations of the setting as a whole. I wanted to draw a line in the sand as to what was appropriate and what was not appropriate for the setting. I am focusing on verisimilitude, so I have to adhere to content for the most part grounded in reality.

The fourth step was to routinely reread and edit old content. As a setting continues to grow, one should take to effort to ensure the pieces all fit together properly. I will take every other month to return to older content in order to ensure the old material lines up with the new material. If older material requires an edit, I will copy it over into my monthly notes for updating. Doing this will always give you something to improve, even with a well-established setting.

My final step continues to come with scale. If you are bored with one region or aspect of a setting, find a region or aspect that has been underdeveloped or set aside. Consider the setting's history and how it has varied throughout time. If you have fleshed out a decent amount of content in the setting's contemporary period of time, consider moving the timeline forwards or backwards to a new period of time.

I hope my tips can help you out in staying focusing with your setting.