Galaxy demo units DO HAVE OLED displays. Is there anything that suggests the OLED displays on demo units are prone to burns but the ones that are sold are not? And of course is great indicator of quality, don't be dump! That's why they are there, so people can make a sens of what the heck they are paying for. A display technology that have screen burns at shop can also have screen burns at home, unless they use a different tech display for the ones you buy.
So yeah. they are still prone to burs, regardless if they are in the shop or in somebody's pocket.
What I'm saying is that a demo unit is always on , that is not normal operating behaviour for a mobile phone.