Take Breaks! A Simple Way to Improve Your Heuristic Evaluation Results
http://www.usabilityprofessionals.org/upa_publications/upa_voice/volumes/2005/june/take_breaks.html

Faulkner, Laura
Usability Professionals Association
2005

Abstract:

As primary tools in the usability field, heuristic or expert evaluations can be rich areas for methods studies and improvement. Early results of one methods study suggest that performing evaluations in limited segments, with breaks between each segment, may increase the effectiveness of the evaluator in identifying usability problems.