Yeah, same here. I vape all day and almost never use more than 2ml.
I think it is a bit device dependent. On my CE5s with my Ego-C batteries I am around 1.5 ML a day. On my Vamo with my protank I hit 3ML a day. Of course I am running my vamo on a much higher wattage and I think it just burns more juice on a firing.
I could be wrong but that is what it looks like to me.