SeaApes Thank you! Yeah, you've got it pretty much right. I'm glad to hear it 🙂
There's currently no way to replenish waiting time. I could explore some replenishment mechanics, but as of now, once you use it up you're pretty much cooked. Not entirely though.
There are actually two ways around it.
First, the light still shifts in real time but much slower. Theoretically, you can wait it out. That sounds somewhat boring but could be appropriate for this kind of game.
The second thing is more interesting. The Remnant is triggered when the last window's shutter is completely down. There's a short time between clicking on the window and its full closure, in which you can escape the room if the window is close enough to one of the doors. The Remnant won't chase you outside the room, but if you re-enter the room - you're dead.
Initially I considered this a bug but turns out it's a neat tactical element. You close the Remnant infested room and stay alive at the cost of the room becoming deadly. The map is mostly loopy (with some blind alley exceptions) so there's almost always the way around a room. The only thing that needs to be added is some visual feedback of a "live" Remnant it the room.
Regarding minimap highlighting, I first thought marking the room status would make things too easy, but it's probably a good idea. We all know you can never make a game too easy 🙂