I have the ViVi NOVA 3.5 ml tank from Vision and I when I "fill" it up, I probably only put about 2.8 to 3 ml in it, never fill it all the way up. This seems to last me about 2.5 to 3 days so I guess I'm vaping somewhere around 1 ml a day. Also, it probably depends on the day. Stressful days lead to more vaping, busier days lead to less time to vape so less vaping.