Confirmation needed. Max money/value per account

[DragonRider]

I'm interested to know how much money/value is safe to have on an account. Is it safe to have 7 characters on a single account, with each character's total value being below 1bill each? What about 7 chars with value 2bill each?

To elaborate, I know there is about a 2 bill credits (or credits plus ship and equipment value?) limit per char. So I don't go past that. That's fine. I even only keep 1b credits per char.

However I've heard people recommend you only use 6 out of the 7 character slots per account. Is there truth to this? I do want to use 7 characters, as I already have enough accounts as it is.