One thing I've found is that it up to each person. In Minnesota where I am, 16mg is about the most common strength that you will find. 1-2ml a day is about the norm here using a pen style clearomizer. As a general rule, whatever amount keeps you off the analog sticks and keeps you happy, then that's the right amount for you.
As for me, in a clearmizer, at 16mg, I go through about 2ml a day. If I'm using an rda, at 0-1mg, I can go through 4-6ml in a couple hours. Using the Atlantis tank only for the day, I go through 8-10ml at 2.5mg. With a kayfun, at 10mg, I go through about 5ml a day.
As for me, in a clearmizer, at 16mg, I go through about 2ml a day. If I'm using an rda, at 0-1mg, I can go through 4-6ml in a couple hours. Using the Atlantis tank only for the day, I go through 8-10ml at 2.5mg. With a kayfun, at 10mg, I go through about 5ml a day.