I have been self-studying for some months now with Minna no nihongo. I am finishing now the first book, and as Noken exams are coming next July, I am having a hard time deciding which level I should take. I mean, I think I can finish Minna no nihongo 2 in a few months, seeing how many hours I spend normally studying Japanese, but I don't know N4 is worth the risk now. (I don't use MNNH only, I'm also revising with Genki I and Speed Master N5)