i have been told that most of the top b-schools require around 3-5 years out---but it does vary with what job you take on and how well you do. An average score can be pushed up with success in the business world.
But JD/MBA they will allow around 2 ....thats why I assume many apply to law school first then MBA afer the first year (if already taken a year off in between---can do well with JD and show that you are smart )
Personally, i decided to do a busines concentration instead of a JD/MBA. I already have a business degree from undergrade and have been told that i will be able to take many of the same b classes as a MBA while getting a stronger legal education. But, I guess it all depends on what career you want to pursue