Thinking about last night's post a bit more coherently, the principle of 'grinding'/leveling up is also very prevalent in real life. I'd say in most cases your education and first (maybe also second) job determine what you will do for the rest of your life, simply because you've become better at it than anything else. Or, in RPG terms, if you start leveling up as an archer it makes no sense to suddenly switch to knight. But if you keep following the same course for the rest of your life you'll end up being unable to do anything else.
Specializing in multiple skills is one way to avoid the leveling up issue. For a web developer example, you could do Django but also Drupal, Angular, Canvas, J2EE. But why stop there? Why not also focus on embedded programming, mobile application development and OpenGL desktop games? You can go even wider. Why even be a developer? Try being a manager, a tester, a UX guy, a designer. Or a fisherman, garbage collector or builder. Sure, you'll have to level up all those new skills, but the first levels are the easiest. Plus, any 'side-skill' you acquire will help you improve your main skills as well. As an example of this I would mention my travel experience and living in Japan, which in practical terms has helped me understand people better, which can be applied in office situations. There's always something to gain.
Specializing in multiple skills will undoubtedly take you farther away from becoming the one-true-expert at whatever it is you do best. But if you just focused on that you'd be grinding in your sandbox for the rest of your life. There's most to life than that, so go out and explore a bit. It's absolutely worth it.