In general no factory can work 24/7 week after week, I never worked at one that did. Machines need maintaining, if you don't stop and do it properly very quickly things break or malfunction. Also when at war, as well as working 12 hrs many were working in other roles as volunteers and others were kept awake by raids and having to move from bombed out houses, some were killed and injured.The British munitions industry went to a 12 hour x 7 day shift at the outset of WW2. Within 2 weeks production was LESS than previous.