I've thought about this too as a student and in relation to professional skills. I call the concept "Engines vs Powerups", due to having played a number of rac

I've thought about this too as a student and in relation to professional skills. I call the concept "Engines vs Powerups", due to having played a number of racing games as a child where you can spend prize money from races on improvements to your car or other items between levels. It's a spectrum, too! Computer languages fall in the middle. Knowing PHP is a lot more durable than knowing Drupal, but PHP probably won't stay relevant as long as Spanish will. One thing I'd share, is that I've gotten a lot of mileage out of skills that were once hot and are now useless. In fact, part of how I got my first well-paid software job at Groupon was because I was comfortable with Backbone.js and CoffeeScript! Neither are used much at all anymore, but I learned a lot of other things at Groupon that have helped me since and they opened the door. https://alchemist.camp/learning-machine/engines-powerups https://alchemist.camp/learning-machine/engines-powerups