Procrastination as a Self-imposed 'crunch mode'

This is an article on how doing more overtime, leads to a loss in productivity - http://www.infoq.com/news/2008/01/crunch-mode

Well, obvious, right?

But would you guess that doing 60hr work-weeks every week (rather than as a 'special occasion' thing), leads to so much lost productivity, that it's usually equivalent to working 40hrs a week? That that extra 20 hours is basically just lost time?

This article talks about employers doing it to employees, but as a procrastinator, I think, no, I know, that I do that to myself.

I know if I could just sit down and power through my work, I could leave earlier, have more 'play' and be more refreshed the next day. But because I've been on half-speed all day, or screwing around, I have to stay late to 'get caught up', and so the cycle continues.  I know I should be better about putting limits on myself - clearly, I'm not currently, but that's why I am where I am.

Dealing with that habit looks to me like the point of the 'Uschedule' from Neil Fiore's 'The Now Habit'. I've read the outline of that book, but now I've got a copy, I need to re-read it, and see if it can give me advice on setting better limits in my own life.

Alternately, what if I just have a shorter attention span? It talks about 40 hours being the 'optimum' for most people, but what if 30 hours is my weekly optimum, and I'm always going to be putting in 50 hours to try and get that 30 hours work done? How do I figure out what my non-distracted optimum amount of work would be, or how do I increase my attention span so I can stay 'on task' for 40 hours?