No mentally healthy and fully lived life can be achieved with a 40 hours work week schedule.
The 40 hours American Industrial standard is based on a neoslavery imbalanced life, barely surviving to continue production.
Europe did better with a 35 hours work week.
Ideally, I would say 25-30 hours week should be the maximum, if a person is practicing deep work, using tools such as Pomodoro or 30/30. For cognitive work, Research shows they will be more productive!