An amusing sample of the prose:<p><i>Most usability studies last from 1 to 2 hours because it&#x27;s hard to recruit users to come in for longer tests. In fact, unless we&#x27;re testing kids — for whom an hour is the max — we usually limit our test sessions to 90 minutes. People tire after an hour or two.</i><p>Wonderful stuff, as is the norm from the Nielsen Norman Group.