Some TVs have a default screen saver which will activate after 2 hours of TV use if no interaction is detected.
If you stop seeing the art being streamed because of this, go to your TVs general settings and disable the screen saver option:
General > System Manager > Auto Protection Time (Samsung)
Settings > Device Preferences > Screen saver > When to start > Never (Android TV)
You may also be interested in How to prevent the TV from turning off by itself while using WindowSight