Ask HN: Do you know anyone who can sustainably code for 30+ hours a week?
When I say code, I mean it though. Daydreaming, looking at HN, answering emails, trips to make coffee - all that does not count.
This is exactly how I try to do estimating as well, plan on 6hr days for productivity, and tasks are never less than a 1/2 day no matter what anyone says. Even the ten minute task for updating that 1 line of code turns into a few hours by the time you have tested, deployed, communicated and documented the update. And in the few rare times it turns out to be a less time, the bonus time makes up for the some of the tasks that will inevitably run longer.