About 45-50 minutes of practice. Did this entire matching quiz:
N4 Matching Quiz
I scored 99%, but only one really "wrong" - where I didn't know the kanji. The problem is sometimes you'll get "why?" and "why?" for possible answers, plus 度して and なぜ, for example. Or when I got "word, speech" and "word, speech" and both ~語 and 言葉 and chose the "wrong" one. Annoying, since the error is merely matching the wrong kanji to the wrong slot, even if it's the exact same definition in two spots.
Good practice, though.
