My hubby works in a plant here in Alberta and they have 5 crews. They rotate and have 12 hours shifts where it constantly is operating and as ss mikey said, the only time the plant is shut down is when there is turn around and everyone is out working to get it back up and running.
Their shifts are as follows:
4 nights 4 off,
3days/3 nights 4 off,
then finally 4 days and then 12 days off with a week of training (5days) somewhere in there. IF they could have some kind of a schedule like this, it would run smoothly and everyone is usually rested to go on their next set of shifts.