Burn-in

First, to prevent burnin, don't set the display to blinding brightness. Set it to 70% or lower if possible.

Second, You don't need a video constantly playing. You can set up a folder of several different photos with a reasonably wide range scenes. Then in System Preferences->Desktop&Screen Saver, select Desktop add the folder of images, then set to change the desktop image every so often. I happen to choose 15 minutes.

Then select the Screen Saver pane. Then select the option on when to initiate depending on how long it will there is no activity.

Generally, you can pay Apple, or a certified repair shop, for repairs if the parts are available. The problem is the age of the Mac; Apple does not maintain stores of parts forever and 3rd party replacements are chancy at best.

If the screen is damaged during the warranty period, and if Apple deems it because of faulty workmanship or parts, the repair is at no cost to the owner.

The salient point to remember is the older the Mac gets, the less likely needed repair parts will be available. Unfortunately, the older the Mac is, generally speaking, the more prone to problems it is. And, as with any device of any make, warranty repairs are at the discretion of the manufacturer with regard to "gray" areas such as burn-in might be.