I work in a very ad-hoc sort of way, but I find the idea of an n-hour work week very useful. If I work _n+d_ hours and feel exhausted, or I work _n-d_ hours and miss a deadline, I have an immediate and intuitive insight into what the problem is (the sign) and how big it is (the delta). Essentially it's a metric that I don't have to think too hard about.

I don't work rigid hours. My n-hours approach is a patch for the otherwise vague system in which I do stuff. And I (at least theoretically) don't beat myself up if d gets too large in either direction; if I'm overworking it's a sign that my planning process is out of whack, and if I'm underworking it's a sign that I need to find a way to get motivated or get out.

I view these "do x" blog posts as interesting things to try based on other people's life experience. It might not work for everyone, but I wouldn't pull the "x sucks" card because it's a pretty subjective problem.