I consider myself to be fluent in English... Yet I've never thought of it as 'devoting my life to learning English'. Sure you can argue that Japanese is harder, but I feel like I've already come a long way since starting learning Japanese, almost a year ago.
For English I can't remember how long it took me, and yes English is more readily available in daily life (TV, it's used for commercials a lot, the internet...), but it was several years before I could really use English to say whatever I wanted to say, to understand texts as easily and as natural as it is for Dutch.
Today I'm at the point where I can safely say I'm *more* at ease reading and understanding, and writing, text in English than in Dutch. In speaking, it's still Dutch though, but only because it's harder to create the sounds used in English, for me.
I think it's entirely possible to reach that level with Japanese, without giving up 'everything else'

it will take somewhat longer than those 18 months... (Because input and eventually just *using* the language, for whatever purpose, is what makes one fluent) But I'm 100 % sure it's possible...
Quote:I think he said somewhere that its gotta be like trading your native language for Japanese.
I think that in a way that's partly true. Maybe it's more like gaining another 'native' language. (Once you reach a certain level.)
At times I feel a bit lost 'between' Dutch and English... I want to say something one way, in English... and can't say it in Dutch while conveying exactly the same meaning/feelings... I'm lucky; my sister understand English very well, and my parents will get what I'm trying to say most of the time...
But already I'm noticing that, on the rare occasion I'll think something in Japanese, or have a Japanese word that conveys the *exact* meaning I'm trying to explain... there just isn't always a real equivalent available in both Dutch and English...
... But this is also very fascinating... (And could start a new discussion

) because I realised that language, whichever language, is in a way a *translation* of our thoughts... And in putting your thoughts into words, you'll look for the best 'translation' of your thoughts. If you know more than one language, at times you'll see you have to skip the best possibility (in language B) because you have to use language A at that moment...
... Sorry, just the tiniest bit off-topic.
Savara