But the point is that it totally depends on the person and it's not this hard and fast rule. It's also vague to the point of meaninglessness considering all th

But the point is that it totally depends on the person and it's not this hard and fast rule. It's also vague to the point of meaninglessness considering all the various kinds of technologies and depths within those technologies one might be toying with in their spare time. I would argue that the general intuition that many programmers have about people who code in their spare time is simply a too-narrow view of the picture. It's more about people who are really good at LEARNING, and people who code in their spare time tend to become very good at self-teaching new things and figuring out how different systems work and interact. A developer can be good at learning as long as he or she is practicing learning something in their spare time, but I don't think it has to be a side project (or even technology-related at all) to see a benefit in professional productivity.