I don't see it as hours = productivity. Why are we so focussed on the "40 hour week"?
The problem here is hours=productivity is linear. There's work (i.e. bang away at a rock and progressively chip away, idealistic) and completing the objective (random, non-linear and realistic).
To me getting the job done isn't simply passing the buck so the blame sits with someone else (this seems to be a regular thing and isn't productive) - it's having the task/objective complete regardless of the number hoops.
Back in 1998 I pulled 18hr/days for three months.. at the end I couldn't string sentences together and looking back on it, was only because it was a linear task could it be described as linear. No way I could do that now because the work requires both parallel tracks and creative thinking (this requires 'free' time).
I am a strong believer that people need a balance - work, rest, family, exercise and mental stimulation (i.e. hobbies etc). Individuals focus better, they make better decisions and are happier. The net effect is they're more engaged in how they look after their work.
You'll note I've not said X hours or working A to B. The problem is that beyond the linear task, it becomes blurred.
Also the attitude of the country also plays a part here. In the US it appears they will demand all hours but fail to realise that the actual productivity is far far lower (pace of actual work being done is far slower than the UK for example). It's almost like the companies are in a 1950s mentality - japan is similar where productivity is seen to be linear with regard to hours.
India focuses on the process even if it's detrimental to the actual goal.. something I've seen so many times.. A to B hours following process is the norm..
Now I spend my time part managing (dev, sales, product, project), part being diplomat (vendors, sales and product), part trainer (sales, product, dev), part investigating new areas that the business can look at (product market analysis, sales). That's for a couple of products, globally for dev, sales etc.
I write astro camera software drivers for a UK camera company, I do astronomy, I do DIY, I oil paint, I sea fish, I do exercise, I spend time with the wife, I see friends and take vacation. I watch very little TV (couple of hours max a week).
I set myself a balance but if there's something interesting that I want to progress, i'll do it. It a bit of a mashup but so far it works.. rough balance is about 40 hours but sometimes that extends to 80+ hours other times it lulls.
Then the weekends on top. 
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