... but honestly learning languages early on is a good investment for several other reasons. Not only for social and economical reasons, but also due to it becoming a lot harder to learn languages later on in life (please do correct me if this is a myth).

If you on the other hand stay learning languages during your youth, becoming fluent in a language takes less and less time (at least according to my own experience and that of all of the polyglots I know).

Also I'd say that being able to call on different aspects of your personality is a very valuable trait. If you combine the use of standard associations exercises (and hence have an above average control of your emotional state) with keying different associational patterns to different languages you'll achieve a capacity for holistic problem solving and idea generation that I'd expect to be soaring high above the average levels.