How long does graduate school take?

That depends primarily on two things: what kind of degree you are getting, and how many classes you can go to per semester. Some grad programs can take two years, and some can take up to ten (usually after that you have to re-take classes because they have 10 year limits at many schools). Getting a Law degree going only to night school is going to take a lot longer than getting a law degree going full time during the day, for instance. And getting a Master's degree only is going to take a lot less time than getting a PhD (which usually comes after a Master's Degree). I would say as a gross oversimplification that it usually takes 2-4 years. :) But you should check your program, your college, and determine how many classes you can take each semester in order to know better how long it will take you individually.