It’s a heresy now (good luck convincing your boss of what I’m about to say), but every hour you work over 40 hours a week is making you less effective and productive over both the short and the long haul. And it may sound weird, but it’s true: the single easiest, fastest thing your company can do to boost its output and profits — starting right now, today — is to get everybody off the 55-hour-a-week treadmill, and back onto a 40-hour footing.
I agree with just about all of this, but good luck convincing the people who matter: both management and the rank-and-file. Management wants to get more bang for the buck, so pushes people (especially exempt employees) to live at work. The line worker doesn’t want to appear less dedicated than her fellows, and so an implicit competition develops (which just happens to be in management’s perceived interest).
The loss of quality after 40 hours is starkly apparent to me as a software engineer. It may not be so in more repetitive, process-driven, less creative jobs, but I suspect it still is.