I think how long you study before taking the NCLEX depends on how good of a test taker you are. Test taking usually isn't a problem for me, so right after I graduated from nursing school
, I took 1 week off, then studied (along with some study buddies) every day for 3 weeks, took the NCLEX, and passed. Everyone has their own speed and style. Some of my classmates studied for three months or longer and then proceeded to pass the NCLEX after their first attempt.
IMHO, you shouldn't wait TOO long to take the NCLEX after you graduate, because you do start forgetting material you learned in class. And do NOT overdo the studying - take adequate breaks when needed; I truly believe that it is possible to study too much. Also, the day before you take NCLEX, just RELAX and clear your brain so that the information you will need to recall the next day will come through easily! Good luck!