The thing that was important in my situation was that my working hours were becoming increasingly erratic, and a lot of my coworkers had no idea what I was working on. For instance, there were days when I'd come in at noon, put in four hours at my desk, then drive to the data center and work until three in the morning.
So I was working about fourteen hours but it looked like I was working four.
If you're working for a small company, people will probably be aware that you're burning the midnight oil. But if you're working for a large company, there's a lot of good reasons to be present at your desk from nine to five.
When you're a software engineer, you get a lot of leeway in terms of expected behavior. Especially in silicon valley companies the size of Google, it's easy enough to seem like you're working your ass off, while doing your own thing on the side. It's all about cultivating an image in the beginning and projecting it. People are mostly busy with their own anxieties and career concerns to scrutinize you.
My employer may not have cared about the things I worked on but that's fair game. After all they hired me and they were happy to have me there for years. I don't see the 'extreme' in what I did, more like common sense or self-optimization.
I started gradually reducing the number of hours I worked for 'real' until, a few years later, I found myself working for two hours a day, choosing to spend the rest on things that contributed to my sanity and self-development (on company time). To fill the gap, I would work on my own software projects, socialize with co-workers, do research on things I found interesting and read books.
Needless to say, nobody noticed. I kept this up for a number of years and then I quit. Looking back on it now, those were some of the best, most carefree years of my life. There is nothing like getting paid a competitive six figure salary to mostly do the things you enjoy and not care one iota about corporate management structures.