Interesting comment by Schnitzelfisch.
But I am not sure if I can agree 
From my experience, 8 hours of "work" for a usual day-time job consists of maybe 2-3 hours of focused work per day. The rest is breaks, meetings, checking e-mails, talking to other people, lunch...
For me 2-3 hours of focused work would be a dream. I made an agreement with my boss that I can take break each hours - 10 minutes - to rest my eyes and so on. So during whole day so its about 70 minutes total per day. So what is the rest - work. Sometimes its even hard to focus that much time.
I know some people just cheat and predend they are working. BUt I would rather have 6 hours of productive day and go home earlier than predend working 8 hours.
And some bosses even think that I am taking lots of breaks. For example one boss when I was asking for bigger salary, instally remembered that my breaks are longer than other people ♦ other people to like 5 mins per few hours (at least they predend that they are working because they sit near computer).
Also when I was in one of job interviews, I again say - I want 10 minutes of break each hour. He says - 5 mins are recommended, but ok (they really needed a worker). But I dont like that fact that its only ok. I would like much more if he would say - at least ten minutes you MUST have a break from pc.
Also if using pomodoro techniqye - the breaks become even longer.
http://pomodorotechnique.com/
and I would really like to use it but, I already not feeling confortable having 10 mins each hour break.
Plus they want people to study after work, they dont say how many hours, but they just want. Its not bad, I like to improve and be better than somebody, but I wish they give me free time for this from workday.
I personally haven't found any people who would be able to put 8h of focused work in on a daily basis consistently over a long-term period. Usually even the people at the top level both in poker in business can get in about 6h of highly concentrated work a day (excluding breaks) on a long-term basis.
Comparing poker to job - still I think its different. At poker you must be much more focused. At job when focus becomes hard, you think slower or make mistake, but it is not as costly I guess if you carefully check/test. It may depend on job, but I am talking about programming.
Also: If you would actually be able to play 8h a day (even with breaks included), when would you work on your game? How much time would that take you? Additional 3 hours? Then we're at 11 hours. You also need to eat, shower... How much free time do you really have left?
If I would be pro, I would not want in perfect world to have more thant 8 hour of work+study. I would still want to play other computer games and have other social life, and also want to save my eyes. And also thats why you are your own boss, you can work less and earn more ♦ and let those who think that its imposible to win work their 8 hours - they deserve it for such thinking ♦ thats the point of poker