This is hard to gauge because it depends on your reading speed, comprehension level, and ability to use what you learned.
If you want simply a 500, I think that if you read through each of the guides, you should be able to attain this score. Typically
MGMAT classes run at 9 weeks to go through all of their books and the Official Guide. The courses typically include very thorough analysis and training. But, if you really want to hammer it out, I think you could read them all within 2 or 3 weeks ( including answering the questions at the end of the chapter).
In addition, there may be sections where you feel that you are superior in and may want to skip and this could reduce your reading time.
I really think you could rush through all of them in less than a month and score at least a 500. Best of luck!