That may be the case for those windows. However, in my Leon playthrough I swear to God at some point there was absolutely nothing left in the station to deal with (in terms of regular enemies). The "new" zombies coming from windows are also finite in number I'm 99.99% convinced of it. Unless someone could open up the game in some editor or do extensive data mining to check out to prove me wrong; I haven't noticed some sort of a constant flow of zombies entering the station after a certain number of them do come in. If they do "respawn" per se in some infinite number over time then I'm genuinely very surprised by that because in my playthrough, as I mentioned, once I cleared the corridors with windows a few times (I do remember going through and having to get rid of some 'new' zombies, yes; but no more than maybe 2 or 3 times total) after a while there was absolutely nothing there anymore ever again. Maybe it's tied to difficulty setting; if that's the case I'm not aware of it at this point. But if it is then alright, that's a nice touch too. I played my Leon playthrough on Standard, maybe the whole finite enemies thing changes on Hardcore, or even on Assisted where perhaps there's just way more of them total since they're just very easy to deal with. With this said though, even if new zombies do make their way in the station regularly, it's still very isolated to certain portions in the map, there's a clear radius of "roaming around" they can do after which point they just never go beyond. There's entire sections of the map that will always remains entirely empty of enemies once you clear them. The rooms that are most affected by that are the ones that aren't in the 'contour' / outline of the station, the 'inner' rooms don't have new zombies entering them, or magically appearing in them later on. The only exception I remember of were SOME rare situations where I'd enter a room where say... something like 2 or 3 zombies where in; however, there's a 3rd, or a 4th zombie lying there in a corner that just didn't stand up AND cannot be killed right away. And later on I come back to the room and that one zombie is now alive or comes back to life as I get closer because 5 minutes ago I 'triggered' his coming back to life mechanic by solving a puzzle or two. I do think I had that situation happen a few times, but was still rare overall. Like 90% of the game is on finite numbers. I can only think of Mr X himself and those sewer monsters being essentially a constant presence in the game.