Maybe make deepspace levels slightly more robust?

code/modules/overmap/sectors.dm

@@ -49,6 +49,12 @@
 	LAZYADD(SSshuttles.sectors_to_initialize, src) //Queued for further init. Will populate the waypoint lists; waypoints not spawned yet will be added in as they spawn.
 	SSshuttles.process_init_queues()
 
+// You generally shouldn't destroy these.
+/obj/effect/overmap/visitable/Destroy()
+	testing("Deleting [src] overmap sector at [x],[y]")
+	unregister_z_levels()
+	return ..()
+
 //This is called later in the init order by SSshuttles to populate sector objects. Importantly for subtypes, shuttles will be created by then.
 /obj/effect/overmap/visitable/proc/populate_sector_objects()
 
@@ -78,6 +84,19 @@
 		global.using_map.map_levels |= map_z
 	*/
 
+/obj/effect/overmap/visitable/proc/unregister_z_levels()
+	map_sectors -= map_z
+
+	global.using_map.player_levels -= map_z
+	if(!in_space)
+		global.using_map.sealed_levels -= map_z
+	/* VOREStation Removal - We have a map system that does this already.
+	if(base)
+		global.using_map.station_levels -= map_z
+		global.using_map.contact_levels -= map_z
+		global.using_map.map_levels -= map_z
+	*/
+
 /obj/effect/overmap/visitable/proc/get_space_zlevels()
 	if(in_space)
 		return map_z
@@ -117,6 +136,9 @@
 /obj/effect/overmap/visitable/proc/generate_skybox()
 	return
 
+/obj/effect/overmap/visitable/proc/cleanup()
+	return FALSE
+
 /obj/effect/overmap/visitable/MouseEntered(location, control, params)
 	openToolTip(user = usr, tip_src = src, params = params, title = name)
 

code/modules/overmap/spacetravel.dm

@@ -1,24 +1,24 @@
-//list used to cache empty zlevels to avoid nedless map bloat
-var/list/cached_space = list()
-
 //Space stragglers go here
-
 /obj/effect/overmap/visitable/sector/temporary
 	name = "Deep Space"
 	invisibility = 101
 	known = 0
+	in_space = TRUE
 
-/obj/effect/overmap/visitable/sector/temporary/New(var/nx, var/ny, var/nz)
+/obj/effect/overmap/visitable/sector/temporary/New(var/nx, var/ny)
 	loc = locate(nx, ny, global.using_map.overmap_z)
 	x = nx
 	y = ny
-	map_z += nz
-	map_sectors["[nz]"] = src
-	testing("Temporary sector at [x],[y] was created, corresponding zlevel is [nz].")
+	var/emptyz = global.using_map.get_empty_zlevel()
+	map_z += emptyz
+	map_sectors["[emptyz]"] = src
+	testing("Temporary sector at [x],[y] was created, corresponding zlevel is [emptyz].")
 
 /obj/effect/overmap/visitable/sector/temporary/Destroy()
-	map_sectors["[map_z]"] = null
-	testing("Temporary sector at [x],[y] was deleted.")
+	for(var/zlevel in map_z)
+		using_map.cache_empty_zlevel(zlevel)
+	testing("Temporary sector at [x],[y] was destroyed, returning empty zlevel [map_z[1]] to map datum.")
+	return ..()
 
 /obj/effect/overmap/visitable/sector/temporary/proc/can_die(var/mob/observer)
 	testing("Checking if sector at [map_z[1]] can die.")
@@ -28,6 +28,10 @@ var/list/cached_space = list()
 			return 0
 	return 1
 
+/obj/effect/overmap/visitable/sector/temporary/cleanup()
+	if(can_die())
+		qdel(src)
+
 proc/get_deepspace(x,y)
 	var/turf/unsimulated/map/overmap_turf = locate(x,y,global.using_map.overmap_z)
 	if(!istype(overmap_turf))
@@ -35,13 +39,7 @@ proc/get_deepspace(x,y)
 	var/obj/effect/overmap/visitable/sector/temporary/res = locate() in overmap_turf
 	if(istype(res))
 		return res
-	else if(cached_space.len)
-		res = cached_space[cached_space.len]
-		cached_space -= res
-		res.forceMove(overmap_turf)
-		return res
-	else
-		return new /obj/effect/overmap/visitable/sector/temporary(x, y, global.using_map.get_empty_zlevel())
+	return new /obj/effect/overmap/visitable/sector/temporary(x, y)
 
 /atom/movable/proc/lost_in_space()
 	for(var/atom/movable/AM in contents)
@@ -139,9 +137,4 @@ proc/overmap_spacetravel(var/turf/space/T, var/atom/movable/A)
 			if(D.pulling)
 				D.pulling.forceMove(dest)
 
-	if(istype(M, /obj/effect/overmap/visitable/sector/temporary))
-		var/obj/effect/overmap/visitable/sector/temporary/source = M
-		if (source.can_die())
-			testing("Caching [M] for future use")
-			source.moveToNullspace()
-			cached_space += source
+	M.cleanup()