I think it is also important to remember that the belt system is a fairly new creation compared to the lifespan of the arts themselves. It was originally just used by Kano (judo founder) to help his students tell eachother's skill levels within his own dojo. I would bet it was never really meant to become what is is today. So, while some schools hold training time as an official requirement, and others play it by ear with skill being the dominant factor, it is such a fluidic system that not alot of stock can be placed in it by itself. You have to get to know the Karateka individually to know if the belt he has, he truly earned. And, at the end of the day, the belt just holds your Gi closed anyway. I think it was Rorion Gracie that once said "A belt covers about 10% of your , covering the rest is up to you."