...boy, I was happy if I would learn two per year 
The idea ain't new.
The first time I read about it was in A. Hunt, D. Thomas, The Pragmatic Programmer - from journeyman to master
On the one hand it's absolutely right. Of course you improve yourself by learning new languages. Any new language you learn add more ways of thinking - doesn't matter if it's a programming language, or a natural language.
On the other hand: What means 'learning a language'?
All beginners classes mostly introduce you to the syntax only. I recall what my driving teacher told me:"Having a driving license doesn't mean you can drive. Only lots of driving teaches you that."
Anyway you learn more, so better suiting languages for certain problems, yes. And you better always chose the language fits best for a certain task. But go and tell @$JOB, that the chosen language was not the best choice, better was to use language XYZ...
I have a list of what additionally programming languages to me make sense to learn, so I want to learn them. But I still don't get even started on #1 on my list I figured out to be most important for me to learn first: lisp
But I always find myself either confronted with the need to get deeper in what I already thought I knew, or get 'distracted' by finding I just need to learn another one first to solve a current problem.
So, recently I needed to put lisp on parking position again, while currently I start to get into awk.
The idea ain't new.
The first time I read about it was in A. Hunt, D. Thomas, The Pragmatic Programmer - from journeyman to master
On the one hand it's absolutely right. Of course you improve yourself by learning new languages. Any new language you learn add more ways of thinking - doesn't matter if it's a programming language, or a natural language.
On the other hand: What means 'learning a language'?
All beginners classes mostly introduce you to the syntax only. I recall what my driving teacher told me:"Having a driving license doesn't mean you can drive. Only lots of driving teaches you that."
Anyway you learn more, so better suiting languages for certain problems, yes. And you better always chose the language fits best for a certain task. But go and tell @$JOB, that the chosen language was not the best choice, better was to use language XYZ...
I have a list of what additionally programming languages to me make sense to learn, so I want to learn them. But I still don't get even started on #1 on my list I figured out to be most important for me to learn first: lisp
But I always find myself either confronted with the need to get deeper in what I already thought I knew, or get 'distracted' by finding I just need to learn another one first to solve a current problem.
So, recently I needed to put lisp on parking position again, while currently I start to get into awk.