When I added the IT8951 code to the SlowMovie Python I commented out this line, with the intention of adding it back...

#epd.sleep()

What happened? The display was not entering deep sleep which appears to have caused an early failure :(

New sleep line: 

display.epd.sleep()

Now that the display sleeps correctly, I required the "init" line which I had also removed... 

#epd.init()

 Adding the "run" command seems to work:

display.epd.run()

If anyone knows technically why sleep is required, feel free to comment below! I'm assuming this has to do with the constant charging of the particles that separately create the black and white image, and a constant charge must wear them out?