[xiaoma]

My current strategy has a bit of complexity and might take an entire blog post to explain clearly. The high level view is this:

Skills vary both in how much the market values them and in their durability. There's often a trade-off between these two characteristics. For example, half a year's worth of study in a foreign language or pure math is only somewhat valuable to the market but that value doesn't tend to decrease over the years. Learning AngularJS in 2013, on the other hand, was so highly valued by the job market that it was a great way for junior programmers with no degree to break into a software engineering career.

I believe it's best to generally focus most learning efforts on durable skills, but occasionally when there's an opening, to flop and focus 100% on an ephemeral skill that's highly valued and appears likely to be even more highly valued in the near future. After capitalizing on the opportunity, return to mostly focusing on durable skills.