I know people who drink water, tea, or coffee intermittently all day long, not just as part of a meal. In that situation, when would you say what b'rachot? Assume you made shehakol before the first cup of coffee; does it "expire" after a certain amount of time so you'd need another for the second cup? Or does one suffice until you interrupt with a meal?
Same with the after-bracha of boreh nefashot (especially because it covers so many things). At what point should one draw the line and say it, even though there's always an "I might eat/drink something else soon" possibility.
This site talks about time limits and minimum amounts for drinks that are sipped over time, like coffee, but it seems to be talking about an extended single sitting. I'm talking about someone who gets to work in the morning, grabs a cup of coffee and takes it to his desk, refills it on his way to a meeting, refills it on his way back to his desk, and so on, all day.