I have a LG CX and I can leave both my Xbox and PS5 on for a couple hours without it turning off, infact on my PS5 I can and have left it on for hours, the screen just goes grey. I'm sure I need to change a power setting on the system but meh its fine.
On the xbox my system goes to into sleep mode after a hour of no activity, before that hour is up about 10 mins out it warns me it's about to go into sleep mode, usually my controller is already in sleep mode by that point so hitting the button starts it all over again.
I have mine set at 1 hour and I believe thats default. but it goes up to 4