I’ll start by saying – I don’t know what the best balance is. Then, what can I tell?

The obvious

1. The ratio between our working hours and productivity is not linear. We all know that, nothing new here. If we work 12 hours a day instead of 10 we won’t produce 20% more features.
2. When we need to get more work done, we work more hours.

The almost obvious

What does our productivity looks like during the day?

Everybody agrees about this graph until the productivity gets closer to zero. But is possible to have negative productivity ?

Negative productivity

This is the counter intuitive part, we had encountered it so many times but it’s still hard to accept it. Starting sometime during the day, we do more harm than good – we cause more bugs, produce fragile design and less readable code. Even though our feature might work just fine, we did more harm than good – next week, when we have to extend the feature, we’ll have to understand code of an inferior standard. We’ll fight the design and most likely, we’ll fight the bugs we missed before.
From my personal experience, during the last year I found myself fighting with features for very long hours. Most of the times when I gave up and left the office, the next morning was extremely productive. I could throw away all the mess I made during the previous evening and write nice code within an hour.

Conclusion

The conclusion is very straightforward – when you’re getting to the zone of overwork, Go Home! You’re wasting your time, you’re wasting your boss’s money and you’re planting seeds in code that’ll annoy your teammates in the near future. We all know this is counter intuitive, but working shorter hours makes us more productive.

More thoughts

We have concentrated on the productivity of a single day. A bit more interesting can be to analyze a whole week. Is it possible that working one day less a week will improve our productivity? If we find this to be true, will we act and shorten our work week? If we’d shorten our work week, should we get paid less or more? On one hand we’re more productive, so we should be paid more, but on the other hand, we work less, so we should be paid less. This leads to an interesting question – are we paid for our time or for our results?
There’s a lot to think about here, but we must find first the optimal balance of working hours and days.