I don’t work long hours. Not anymore. Oh, I did long hours at one point. I carried a load and half of physics and math one semester in university along with five to ten hours of practice and rehearsal on the violin. It was awful, and wasn’t the hardest thing I did in university. That honor goes to Lawrence Thomas’s doctoral real analysis course (the math graduate students had given up asking why I was in class with them as an undergraduate). Just for the record, math classes can cause you to wake up in cold sweats from how much rewiring of your brain you’re having to do. I’m still processing material from that class a decade later. I was only taking two or three classes that semester.
These days I do three to five hours of hard, creative work a day, another hour or two of planning, organizing, and overhead, and I usually read or write for an hour or two in the evening. That schedule produces my highest rate of output.
The first thing that happens when people hear that is they start saying how they can do eight or even ten hours of hard, creative work per day. With very few exceptions (I know of three by reputation, none personally) those eight to ten hours are actually three to five padded with reading reddit or thrashing in disorder, or those eight to ten are fine one day, and the next day’s eight to ten produce less, and the next day’s even less…
And there lies the crux of the matter. The time it takes me to do a piece of work varies by an order of magnitude between when I’m fresh and when I’m exhausted. Any schedule that doesn’t leave me fresh the next morning will eventually grind me to exhaustion, and that order of magnitude difference means that three hours when I’m fresh can be come thirty hours when I’m exhausted. At that point I will save time by taking a day or two off.
From long experience, I know that three to five hours leaves me fresh the next day. My anecdotal observations of those around me make me think that I am typical.
“But deadlines!” I can hear someone saying. “Surely you work longer in the crunch time right before a deadline.”
Nope. If there was a time when I had to crunch for a deadline, it’s so long ago that I can’t remember it. It certainly wasn’t in university, and I was homeschooled before that, which meant a noticeable lack of deadlines. Remember when I said I do three to five hours of hard, creative work and an hour or two of overhead? This is where the overhead comes in. You plan your work.
So for software engineers, unless you have data showing that you are one of the rare people who don’t degrade on more than three to five hours a day of hard, creative work, this is your optimal schedule.