how long should i prepare before taking the gmat

Historically, most successfull GMAT a$$ kickers spent 2-3 months of regular preparation. I think thats a good amount of time frame to prepare.

I've been doing about 8 hours a day plus 6 hours on Sats....what do you guys think?

8 hrs a day!!!!!! Thats overwhelming!!! Make sure you dont get tired of it and quit in the middle.. The success depends on consistent preparation rather than breaking your spine!! Although 8hrs a day would be great but you would probably achieve the same score with 3hrs a day during weekdays and 4 hrs during weekends for 2 months.. remember there is a threshold of how much your brain can hold effectively and after this threshold the efficiency tends to go down and your concentration could lessen!!

I agree that 8 hours per day is WAY too much for most people. You may be the exception, but the vast majority of students I've had can't handle more than about 2-3 hours of study per day. Remember: quality over quantity.

A good, sustainable study plan is just that: two to three hours per day, five or six days per week. Be sure to leave time to enjoy yourself!

I forgot to add: I'll agree with the above that about three months is a good amount of time overall.

5.5 days per week x 2.5 hours per day x 12 weeks = 165 hours of study!

That should be plenty!

I agree with Jim here. Although I admire the determination, I can't imagine spending 8 hours a day studying for a test!