The only thing that will turn my brain off is some sort of lean back entertainment, such as TV or video games. Otherwise, why read about how to do something when I can practice it?
It's a fallacy to believe that work and play can't be the same thing.
Come on. There's a big difference between being able to decide what to learn and at what pace, and being told by someone else to learn something as soon as possible so as to get work done.
If you do have hobbies outside of programming, why wouldn't you like to spend some more time on those?
That said, the reason I spend more time programming than anything else is because there is no feeling of achievement like the feeling of having built something.
It's also a fallacy to believe that the majority of workers are lucky enough to get paid for something they truly think is fun.
There are studies that show that work preoccupation outside working ours can be a sign of burnout (incoming or undergoing). I know it's great to love your job, that's what flow state is all about, but there can be a darker side to it as well.
I thought the same when I was in school (a year ago) and was completely into programming and computers. I took all the hard classes and spent 60-70 hours a week studying and doing projects.
But that came at the expense of a social life. Now, I'm in the workforce doing a cool programming job. But, I have exactly no cool friends and no social life to speak of. I had exactly 3 dates in the last year, all leading to nowhere. The loss of social skills and exposure to diverse people (most of my friends are programmers), seems to be quite narrow-minded way to live.
As the old adage goes "Work-life balance: Live to work or work to live"
When your with the right women & have some kids, I find it is difficult not to want to get out of work to spend more time with them.