For the past week, my phone will stay lit up if I don't manually turn the screen off. I checked the settings and it's set for 30 sec. I have also pulled the battery out and tried that. It's sucking my battery down!
We'll help to get your screen to turn off after 30 seconds like you want it to. Do you still have the Galaxy S 4? Do you have Development Options enabled? If so, you may have ticked Stay Awake on accident, and that will override the timeout settings. If not, Smart Stay also overrides the timeout settings so it may need to be turned off.
Was there anything that coinsided with the screen staying on? Anything like a new app or app/software update of any kind?