[JohnFen]

It's true that if you just add up the minutes, then peripheral activities don't take up the majority of the time. But you also have to take into account the cost of context-switching. An hour-long meeting costs more than an hour of time because you have to ramp back up to speed afterwards. On average, this takes about 20 minutes. When you add in all of the distractions through the day -- meetings, people talking in the next cube, people stopping by for a "quick question", that sort of thing, that ramping-up can absorb a ton of time.

[MichaelZuo]

Not for actual or potential super geniuses similar in situation to Einstein at the Swiss patent office.

By definition they spend very little time and effort on 'context-switching'.