No activity for 3 Hours function from Instruction Manual.
//To conserve energy, the TV automatically turns off when no operation of remote and side
panel key continues for more than 3 hours. (Stay on/Power TV off)
Note
•Not in use when "Auto power on" or "On/Off Timer" is set, or while "PC input" is selected.
•"No activity for 3 hours was activated" will be displayed for about 10 seconds when the TV
is turned on for the first time after the power was turned off by "No activity for 3 hours".
•The on-screen display will flash 3, 2 and 1 to indicate the last three (3) remaining minutes prior to the shut-off.