There really is no blanket statement anyone can make in terms of "You should train everything once ever 6 days" because it depends on a number of factors:
-Your training goals (Body building, pure strength, Sport specific, endurance, a specific lift for a competition, etc...)
-Your genetics (Can you recover in 3 days? Does it take a week? Do you need to bring up lagging body parts?)
-Your life (are you only able to get to the gym 3 days a week? Working 60 hours a week? Sleeping 5 hours a night?)
The list goes on and on. The world of BBing has seen TREMENDOUS success with training a body part once every 7 days. There are also many people who have had success with training 6 days a week hitting everything twice (Look up the "Big Beyond Belief" thread)
I know this is not a satisfying answer, but you may have to try out a program for 6-12 months and see how it works for you to know how YOU personally react to it.
Body building is a LIFETIME endeavor, there is plenty of time to try out different methods (in fact, its the ONLY way to make sure you are training optimally for your unique genetics), just make sure to give them ample time to work. When you are 50 years old and have been training for 30 years, the fact that you spent a year trying a new method wont amount to a hill of shit in the end even if it yielded absolutely no gains (which is damn near impossible if you eat and train hard)