Loss of hardware home and navigation buttons
The major cause of 'Burn In' is the loss of the hardware home and navigation buttons. This gives the need to have an 'Always On' nav bar at the bottom of applications. Always the same buttons and same colour, resulting in the burn.
Having owned a Pixel XL for just over a year now, I have complained to Google (yes Google via the provider as their own solution was non existent) about the screen burn in.
Google requested that the provider immediately furnish me with a brand new, boxed handset and send the old one back to them. This has now happened twice, with the exact same outcome.
I understand that 'Screen Burn' is something that they cannot really do anything about due to the design, however id rather have the google handset as Google appear to know a little something about after sales care. (I was told that at any point in my two year contract, i could swap the unit for a new one if i had screen burn as the ombudsman now views the hardware as unfit for purpose)
Additionally in Android Oreo, the nav and home icons change colour depending on the colour of the app screen in the background. This should serve to save the overuse of particular pixel colours and should make the unit last a little longer.