The primary point of this thread is that it is hard to be very productive for 6 or 7 hours a day, let alone 10. Also I gather most people here are talking about working remotely.

I take a long lunch (yeah flextime!) and if at all possible, exercise during lunch, and I have enough simultaneous projects that the silver lining is I do different stuff before and after lunch. I tend to code/deploy more in the morning and design/test more in the afternoon (only a lunatic deploys five minutes before going home, no matter how well tested...) So its more like two separate five hour working shifts. I get the feeling this kind of lifestyle is pretty unusual here and people just code, continuously, for 18 straight hours, and think thats productive, or whatever.

Like most hacker types my home life is more interesting than my work life and I do totally agree with the assessment that its impossible to grunt out even 7 productive hours on one individual task.

(and edited to add that at the cutting edge I don't think its possible to work more than 4 continuous hours. Either its not really cutting edge or you're not being productive. I can do mindless yardwork reinstalling my paver brick patio for 12 hours, but there is no way to be productive when interfacing a new DDS synthesizer to a rasp-pi which as far as I could tell has never been done before, I could sit at the bench for 12 hours but I won't get any more done than just 4 hours, I'm just a little more honest about it than some, maybe most. At home I can do whats "right" not what is "management approved")

Another interesting aspect is a lot of design work is thinking and surfing the net for new ideas and inspiration and I can see from outside my brain that looking fairly unproductive. Or from a noob perspective, noobs not understanding that a half hour staring off into space might save five hours of coding despite not feeling like its as productive.