I keep everything on one toon too. I keep all the ec, Big Notes and stuff for sale on my sin while stuff that is noob related (like different types of mats and primal/arena gears) is kept on my mystic.
He said he doesn't carry any ec on his main, not alts.
Anyway, I always keep at least 100 ec and 20 million coins on my alts, just in case. You never know.