THE IDEA of working 12-hour shifts never seems too appealing. Indeed, one school of thought believes that such long shifts must surely lead to staff exhaustion and exhausted staff are bound to make more errors. As sure as fate, sickness levels will rise and, therefore, so will spending on agency staff to provide cover. All of which sounds extremely plausible, especially for those of us who have never worked the dreaded dozen-hour shifts. But is it all true, or has a myth grown up around 12-hour shifts that has no basis in fact?