I don't think it takes that long if you really study four hours a day?! That is A LOT of time! Of course, it depends on how well you learn new languages, some people pick them up quickly and some take a lot longer to get comfortable.
I've been studying Korean for almost two years now at a very casual pace. I have an hour-long lesson about once a week (I skip weeks here and there) and just write diary entries if I feel like it (maybe twice a week?). The most contact I have with Korean on a daily basis is probably social media, reading tweets or Instagram captions. It doesn't add up to a lot is what I'm trying to say, haha. And despite this casual pace, I've made a LOT of progress in the last two years. Seriously, a lot. I read books and actually know what I'm reading. Same goes for news articles or subtitles.
I'm 100 % sure that if I had consistently studied for four (or even just two!) hours a day from the start with the same methods I use right now, I would be fluent by now. It's still different for everyone and it also depends on how you spend these four hours of study time, but... how could you not make progress if you're spending so much time on a language?
I'd be extremely interested in your methods, by the way! What do you usually do every day? Do you read articles or watch videos or practice writing or just memorize vocabulary? :)