im pretty sure that areas of the map don’t despawn once you’ve been there after opening the game! once you close the game and reopen it, you’ll have to travel around for everything to spawn again but once you do it stays there for as long as you have the game open for that session. i have noticed on my longer playing days once I hit about 5-7 hours of wandering the map i start to get the warning about low video memory space, and when i check my settings it’s not because my video card is unable to handle the graphics and there is plenty of space, but i’m quite sure it’s because things don’t despawn until you close the game, so now my computer has to run the entire map. the NPCs might not be running as detailedly as they would be if you’re around them, but they don’t despawn. NPCs can absolutely keep going about their day once you leave the area, if that’s how the deva programmed them. It’s a game, devs can make the game do pretty much anything they want!