I usually do it when I have school activities: homework, thesis and so (high school, university, I think even elementary and middle school, but it became an habit in high school). Three days and a few hours is my longest period, it was in high school. It was kind of scary, I hallucinated... or did I? Since then I think it has been less than three days, like two days and some hours. Normally, it's related to school work, but I can't deny manga and anime have been a nice excuse.
