I wish I kept better track.  When I first started I think I used about 2 ml's a day.  Now I am constantly switching flavors.  I know I have used at least 1ml from one device today.  So I would guess around 3-6 ml's a day.  I would like to get exact measurements, as I have a buddy I am talking into getting into vaping, and he was wondering the same question.  Time for some better calculations.  I do have some left of an 18ml bottle of ecto plasma from Juicy Vapor from 10-15-12.  And I vape that semi regularly.  With some many flavors, and different cartos, clearos, and tanks, I lose track.  I do not think my rambling is any help, except maybe to me.  Hope your trip works out for you and you find a decent supplier there.  Good luck.