Previous research hypothesizes that long working hours are related to consumerism, the ideal worker norm, high levels of human capital, and a high cost-of-job-loss. The authors test these hypotheses using panel data on working hours for an Australian sample of full-time employed workers. Analyses include a static cross-sectional model and a persistence model for long hours over time. The results suggest that long hours (50 or more hours in a usual week) are often persistent, and provide strongest support for the consumerism hypothesis, with some support for the ideal worker norm and human capital hypotheses, and no support for the cost-of-job-loss hypothesis. Other results are consistent with a backward-bending supply of long hours, and with multiple job holders and the self-employed working long hours.