Here is what I would reply: I'm 43 years old, been programming all of my life, and have a Master degree. I've never seen a person do concentrated work or study

Here is what I would reply: I'm 43 years old, been programming all of my life, and have a Master degree. I've never seen a person do concentrated work or study for more than 6 hours a day. I've met plenty of people who claimed to do double. But they were either lying to me or to themselves. If you think people can do 50 hours per week of highly concentrated work, you still have a lot to learn. Once you understand developers have around 0 to 6 hours of productive work in a day, you can start to optimize it. Best of luck to you!