I'm probably using about 4-5mL per day. I tootle away at my Smoktech Micro ADC II tanks during workdays, and that keeps the consumption down a bit. At home, the Nautilus Mini and Kanger ST Nanos get more use. I might do 6mL on a lazy Saturday.
One time, I snorkeled down 10mL of Strawberries & Cream from Vape Wild, a little freebie sent in 3mg strength. I normally use 12mg so I had to blow heavy. And that was using my little Smok tanks! I had a sore throat the next morning, though.