Japanese isn’t stagnant. Despite being around for thousands of years, it is in a constant state of flux. Even more so in recent years with the information revolution and the invention of the Gyaru.
On top of that, to keep up with a language you have to keep up with the country’s culture, and how it also changes. Finally, to add one more time consuming hurdle, you have to keep up with the news which as you know from your own language becomes a daily job in itself.
None of this is actually a problem if you love the language and the country it comes from, as it becomes a natural process. As long as you keep watching and reading and listening to new material from that country, on a daily basis, your Japanese ability will progress with the language itself.
However, don’t forget you are keeping up with your own language and culture and possibly another if you are going for multilingual. With all this you can see the time commitment starts growing.
You really have two options
1. Fall behind
2. Make the commitment
Falling behind isn’t a terrible thing. It just makes you out of touch with modern culture, and the language that is coming out of the culture. Make the commitment and you get to move forward with Japan, which is quite rewarding. It’s a great feeling to know the Japanese that was used, the Japanese that is used, and most importantly why.
All of this is the reason why people say you never stop learning a language. It’s not that it takes that long to get good or Japanese is some super impossible language. Japanese people never stop learning Japanese. You never stop learning period.
But that is part of the excitement of it all. Don’t ever consider it a burden. Consider it a privilege, and one that you’ve rightfully earned.