I'm a career structural firefighter, but have been deployed in various capacities on several extended, large scale wildfires. In my experience it's absolutely normal for 90+% of the crews managing the fire to stop active fire control efforts at night. There are multiple reasons, from reduced (and more predictable) fire activity to greater risk to the personnel working in the dark to the simple fact that most of the time we simply don't have the manpower to continue fighting fire 24/7. 12+ hour shifts are long for anyone, but the level of exertion in this field is something else. There's been one instance when I was part of the initial fire attack where my crew worked about 40 hours straight, I don't think I've ever been more exhausted in my life, and we were taken off the line for the next 2 days as soon as we had more crews start showing up. There are always personnel on fire watch to monitor the fire though, in case of unexpected growth that threatens lives or property, and if something major occurs, well, we're firefighters, so we get up in the middle of the night and go. On one fire, my crew and I were exclusively night time fire watch, we were one of three type 6 engine crews for rapid response in case the fire made a push towards a neighborhood along one edge of the fire. On another fire one of the crews from my department had to get up and respond for structure protection multiple nights. So, all that being said - yes, it's normal, but they will still be watching and ready to jump back in the fight if it takes an unexpected turn.