The rooms with SmokeDetector have an advantage - if a spam post is detected at least once in 14 days, the message from SD prevents the room from getting frozen.
At the same time, it saves a bit of work for the mods - in some cases, those chatrooms would need to be unfrozen.
My personal opiinion is that it is worth to keep at least the main chatroom for the site open. (Although I am aware that in some cases the main room goes without any messages for several months - typically on smaller sites.)
