The cast dies because the stick reboots itself overnight, most often between 02:00 and 03:00, and a cast never restarts on its own. No setting holds a session for weeks. Render the page or playlist on the screen side with a signage player, and the nightly reboot brings the content back with no re-cast.
The cast from your PC is not failing; it is being ended. A consumer cast stick schedules its own reboots, most often between 02:00 and 03:00 by operator reports, and a cast session is a live connection that dies at the reboot and never comes back on its own. At 07:00 your TVs turn on to a stick that restarted hours earlier and fell back to its screensaver. No menu setting holds a cast for weeks, because the reboot is not a setting. The durable fix is to move the rendering onto the screen side, so a player loads the page or playlist itself and the nightly reboot brings your content back instead of killing it.
What ends the cast overnight
A cast is a live session with two ends: the sender, a tab in the desktop browser on your PC, and the receiver, the stick behind the TV. The stick has its own power supply, so it stays awake while the building is dark. Consumer sticks fetch firmware updates and housekeeping tasks in the small hours, and the restarts land most often between 02:00 and 03:00. When the receiver reboots, the session is gone. The sender never re-casts: the tab on the PC keeps rendering to a receiver that is no longer listening. At 07:00 the panel comes back to a freshly restarted stick showing its screensaver, which is exactly the morning you are seeing.
That timeline also explains why the screensaver setting never saved the session. Ambient mode takes over only after the session is already gone. You are not fighting a timeout on the screen; you are fighting a restart at 02:00.
What your 30-minute test already proved
Your TVs run on a 07:00 to 16:00 timer, so the obvious suspect is the TV. Over HDMI, video travels under HDCP, High-bandwidth Digital Content Protection, a handshake in which the source authenticates the screen before it will send a picture. With the panel powered off there is nothing to authenticate to, and many receivers end the session at that point. That theory fits a sign that dies while the building is dark.
Your own test clears the TV. You switched a panel off for 30 minutes, switched it back on, and the cast was still live. Thirty minutes of dark panel left the session intact, so the timer and the HDCP drop are not what is killing yours. That leaves the stick, and the 02:00 to 03:00 reboot window matches a sign that is dead every single morning.
What the stick's settings can hold
Set the stick's ambient, screensaver mode so it never takes over, and use the keep-awake option in the developer settings where the model offers one. Those two stop the screen idling during a session. They have no effect on the overnight reboot, because firmware updates are not a user setting on a consumer stick.
For a hung session, the maker's reset instructions are a power cycle: unplug the stick's power adapter, wait 1 minute, and plug it back in. That clears the stuck state and nothing else.
Field reports from operators who ran sticks as signs put an unattended cast at roughly a day before it drops, with two days rare. The same reports describe sticks that ran this way for weeks beginning to drop quality and reboot at random, and heat is the usual explanation: a small sealed case has little surface to shed a running chip's heat. Casting is built around someone pressing play for a film or a meeting. No combination of settings turns it into a sign player.
The layout that survives the nightly reboot
Put the rendering on the screen side. A signage player, built into a signage display or running on an ordinary TV as an app or a separate box, loads the content itself: a playlist from a card or internal memory, or the page pulled from a web address on a schedule. The PC and its browser leave the chain entirely, and the nightly reboot starts working for you: the device reboots, and the player is designed to come back up with it, so your content is on screen before anyone walks in.
The stick-versus-player trade is covered in streaming stick or a dedicated digital signage player, offline playlist autostart on a signage screen walks through the power-on behavior, and smart TV app or a separate player weighs the TV-app version of the same choice. A player built for the job can also be locked down so the sign is the only thing that runs, as in this locked-down signage player on an embedded board.
Our panel-mount displays work this way. The free player runs on the screen, plays JPG, PNG or WebP images and MP4, M4V or WebM video from microSD or USB with no subscription, and keeps a copy of the show in internal memory. Set up as the home app, it brings the show up full screen at power-on, and if the app stops it is designed to start again within seconds and go back to playing. We publish no duty-cycle rating for these units, but a sign that must be up when the building opens is the job this layout exists for; see the lobby displays for where it fits a building entrance.
The TV's 07:00 to 16:00 timer moves into the player too: set the display on and off daily, and outside those hours the screen shows black at minimum brightness, because the app has no way to switch the backlight off.
Be clear about the one job casting handles and a standalone sign does not: a page that exists only on the PC. A screen-side player shows content it can reach over the network or load from files; it cannot mirror a tab. Publish the page to a web address the player can load, or export the layout to image and video files, and the cast disappears from the design.
Worked example: a cast restarted at 07:00 against a 02:00 reboot
Inputs. The TVs come on at 07:00 on the 07:00 to 16:00 timer, and the cast is restarted at 07:00 each morning; both come from your setup. The reboot window, 02:00 to 03:00, comes from operator reports. There are two sticks, also from your setup. The calendar basis is 5 weekdays in each of 52 weeks, 260 working days.
Rule. A cast lives from the moment it is restarted until the first overnight reboot. The reboot ends the session and nothing restarts it, so the longest the session can be is the gap from 07:00 to the reboot.
Arithmetic. 07:00 to 02:00 is 19 h. 07:00 to 03:00 is 20 h. The session therefore dies every night at 19 to 20 h of age, and each death costs one manual re-cast the next morning: 2 sticks x 260 working days = 520 restarts a year. The panel hours add nothing to this: the timer powers each panel 07:00 to 16:00, 9 h a day, leaving 15 h dark, and your 30-minute test showed dark hours leave the session alive.
Result. Best case, a 19 to 20 h cast per day and 520 manual restarts a year across the two screens.
Decision. Any page you can publish to a web address, or export as image and video files, moves to a screen-side player, where the nightly reboot ends zero sessions and costs zero restarts. Keep a cast only for a page that exists solely on the PC for the length of a meeting. If a cast really must carry a sign through tonight, automate the morning re-cast from the PC and budget for it to drop again each night.
What to change first
- Decide what the sign shows. A page with a fixed address, or content that can be exported to files, belongs to a player.
- Pick the screen side. How to choose a digital signage player covers the options, from a player built into the display to an app on an existing TV.
- Move the hours. Set the daily on and off times in the player and retire the TV timer.
- Leave the PC out. Once the player renders on the screen, the casting PC goes back to its day job and the 02:00 reboot becomes irrelevant.
Recommendation: keep casting for meetings and temporary pages, and move any sign that must be up at 07:00 to a screen-side player this week; if the page lives only on the PC, publish it to an address the player can load or export it to image and video files first, because that single change removes all 520 manual re-casts a year from your calendar.
Questions
Can I automate the cast so it restarts each morning?
You can, as a workaround. A script or scheduler on the PC can start the session again before the TVs come on at 07:00. That ends the morning chore, but the stick still reboots overnight, so the session still ends and the automation still has to restart it, every night. If you are writing a scheduled restart, you are one step away from loading the page on a screen-side player, which removes the restart entirely.
Does a TV with a built-in cast receiver avoid this?
It removes one reboot source, the stick, but not the weak architecture. The TV's own system still updates and restarts itself, and casting is still a session driven by the PC. Whether the receiver is a stick or the TV itself, a sender somewhere has to keep the session alive. A player that renders on the TV, as a TV app or a separate box, is the steadier layout.
Why does a cast stick degrade when it runs as a sign?
Reports from long deployments follow the same pattern: after weeks of running, the stick starts dropping quality and rebooting at random. The case is small and sealed, with little surface to shed the heat a running chip produces, so the silicon sits hot hour after hour. That heat load is what shows up as random reboots and picture drops. Dedicated signage players spread the same electronics over a larger case.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.