I think that people get used to working certain hours. If they change their hours by increasing their hours or changing when they work, this could be a problem to someone’s health. So if someone starts working a night shift at their job, they may feel more tired and have less energy for a period of time. They may also have trouble focusing and thinking during this time.
After a while their body will get used to this new time of work. So they should not go back and forth of when they work. Also if you are not used to working long hours every day, then the first few days would be problematic. After that when you have worked those long hours for a few weeks your body will adjust.