I've been wanting to learn Japanese for a while now, but I have too many other side projects to dedicate study time for it. How long did it take for you to learn the necessary skills for the N5 and N4? Were you also taking classes?
JLPT N5 and N4 are relatively easy. I studied Japanese in high school. I should have got my JLPT 3 (Jlpt 3 is now the N4, jlpt 4 is N5) few years ago. So I didn't study for my N5 or the N4 and I barely passed, the passing mark is 90/180, I got 101/180. Had I signed up for the N3 I would have failed miserably.
I am planning to do the JLPT N3 in this December. N3 is the new level between the old 3 and 2. It's around 600 Kanji and around 4000 vocabs. So pretty I have to study around 8 new vocabs and 2 Kanji a day from today to be able to pass N3. I was planning to do the N3 in July but looking at the requirement, there is no way I can pass N3 with my current ability.
according to wiki
Level Kanji Vocabulary Listening Time of Study (est.) Pass Mark
4 ~100 (103) ~800 (728) Basic 150 hrs (A Basic course level) 60%
3 ~300 (284) ~1,500 (1409) Intermediate 300 hrs (A Intermediate course level)
2 ~1000 (1023) ~6,000 (5035) Intermediate 600 hrs (An Intermediate course level)
1 ~2000 (1926) ~10,000 (8009) Advanced 900 hrs (An advanced course level) 70%
so if you want to study Japanese, you should book in for the JLPT N5 test this July, N5 is extremely easy. only 100 Kanji and 800 vocabs. If you're Chinese or Korean. You should be able to pass N5 with little effort.
Another you have to remember is even if you pass Jlpt N1 it does not mean you can speak the language. It merely means you can read, listen and understand Japanese. JLPT does not test your speaking or your writing.
It's a great language to learn if you want some fun, but Japanese is not as appealing in the business world as it once was. If you're not a Chinese, and want to study a new language. Chinese is the way to go, trust me on this one. Mandarin will be as useful as English while Japanese ain't that usefully.