It depends on the nature of your job. Very early in my career, I had a job manning the tech support line for an ISP. That's the sort of role where you have to be in your seat in case the phone rings.<p>Even if you're not in a reactive role like sales or support, it may be important to be around and available to interact with or be consulted by your colleagues. In large organisations, it's rare for people to work entirely in isolation. They're usually part of a team or wider group that collaborate. If some members of the team/group keep strange hours, that can lead to delays (e.g. a quick question could end up not being answered until the following day). This is one of the downsides of offshoring work to different timezones.<p>It's very easy and glib to say "If you're not being productive, just go home!" - and that may well be the right thing to do if you work for yourself - but keeping regular hours greases the wheels of large organisations.<p>Besides, there are alternative methods of clearing your head. Early in my career, I found that the solution to a tough technical problem would often come to me while I was having a cigarette. I realised that the act of stepping back from the problem was what allowed me to solve it. I don't smoke anymore but I frequently get up from my desk to go for a walk around the block, pick up a coffee or just go do a bit of window-shopping for half an hour. Then I come back to my desk, refreshed, productive and still available if my clients/colleagues need to speak with me.<p>Sometimes, I don't even need to leave my desk - I just do a bit of web-browsing and read some discussions on HN. :-)