I shoot for eight "very product hours" (+2) per day. Even though the standard workday is considered eight hours, it's pretty difficult for me to hit such a target without invest 10-11 hours of what I would call pretty distraction free work. I'm self employed, so I'm able to avoid a large amount of the normal worktime lost to meetings, chitchat, and the like.
Comparing eight hours of "very productive" rescuetime output feels as if it would be comparable to about 12+ hours standard in a normal work enviroment.
Often, when I hear people exclaiming that they've put in a 70hour/week or whatnot I wonder how many very productive rescuetime hours that would correlate to... 50? 40?
When you are at work, do you work. You shouldn't be browsing reddit or checking facebook/twitter or fantasy football/espn. You shouldnt have a chat client open with friends/family (create a work only one)
At our office we are allowed (and encouraged) to read tech blogs such as hackernews, but no one abuses that and reads for hours on end.
We use RescueTime and part of our 8 hours includes email, irc (work #channel), instant message (work only 'friends' screenname), reading rss on top of the actual coding. No one is looked down on for having a high google/stackoverflow time in a week.
Two 4 hour blocks of coding is not that hard (and normally broken up with meetings or some form of communication anyways)
I find people that have to work 10+ hours to get in 8 actual work related hours are the same people who used to "NEED music" to study. Just have some self discipline and focus.