In the beginning of my freelancing career, I never understood why people who bill for their time (lawyers, other freelancers) seem to always bill in 15 minute increments or more.
I understood one argument: that you have some “charge-up” time that is lost when you switch contexts. Switching from one project to another seems to take about 10 minutes of getting accomodated with what you’re doing.
I’ve found another benefit to billing in 15 minute increments: getting “un-stuck”.
I avoid stopping work at something like 4:08PM and rounding up, just because it would cost those extra 7 minutes to the client without benefit. I’ve noticed that unless I have some other pressing engagement, I usually want to stop working when I’m not performing well. Usually, I’m not doing well because I’m stuck on some piece of software.
However, because I need to keep on working for at least 7 more minutes - I often find a solution, or at least lose that feeling. I end up staying in flow longer, and end up delivering more value to the client.
Without this arbitrary restraint, I would’ve quit.