The Pomodoro Technique uses periods of fifteen to thirty minutes, and the traditional period they'd use was twenty-five minutes.
http://pomodorotechnique.com/I notice that when I'm doing housework and I time the bursts of activity, they usually end up being more than twenty-four but shy of twenty-five minutes.
I came up with a method similar to The Pomodoro Technique that's somewhat inverted: I try to work on something for at least twenty-five minutes without getting distracted or even looking at the timer. If I'm pretty confident that I've worked for at least that long, I go back to the timer and check. If I fell short of twenty-five minutes, I reset it and try it again immediately. You then have an incentive to stay focused for that long and not be distracted and you may find you've done more work than twenty-five minutes (it's not uncommon to get almost thirty-five while you think you've done twenty-five).
I had a few influences in coming up with this system:
The Now Habit by Neil Fiore, where he tells you to keep track of how long you spend on tasks on which you typically procrastinate to track your progress, but tells you not to count them unless they exceed some set period you decide (I think his is between fifteen and thirty minutes) in order to keep you focused. I was also influenced by a study that I saw about the 10,000 steps program, where it noted that people walked more steps if they had a step counter with a cover on it to keep them from looking at it throughout the day (but I can't remember if they were told
not to look at it, or if just using one with a cover made people less likely to look at it). Nonetheless I find I tend to work longer stretches if i "gamify" this effort.