Taking the JLPT 2 this year
(note I said taking, not passing!!)
It's just a matter of kanji for me. And getting enough reading practice in.
As for the hours/years of study debate, when I first asked my Japanese teacher here how long it would take for me to prepare for the JLPT she said it's about 2 years for a Westerner but about 1 year for a Chinese or Korean person. Gah.
I'm taking it after a year but, as I said, I don't know if I'll be ready or not but also I'm living in Japan now so I'm learning fast and getting more practice than someone sat at Cambridge University reading grammar books all day.