Hello,
Your assumption was correct as you can send a screen to EVE and it will persist until you draw the next screen or power down etc.
You should not need to re-send your display to refresh the screen unless you want to change the screen content.
What does your MCU/SPI bus do once you have sent the screen? Does the SPI remain completely idle or are you performing other operations (even to other SPI devices if they share the same lines with different chip select)?
If you stop sending any SPI commands after the screen is complete and displayed, does it make a difference?
Also, ensure the chip select is de-asserted when not taking to the BT816,
Best Regards, BRT Community