Well, it was probably around 2-3 times a day, I am using much lower wattage and hence, less e-juice, which is the reason for higher nicotine in MTL tanks, you are going to blow through way less juice. It's an easy topfill though, which makes matters more pleasant. With that said, I now own a kabuki, which has to be the easiest bottom fill ever... But typically, I go through about 6-7 ml of juice per day max, and that's on a really bad day.... So you won't have a "drinking juice" problem the same way you would with a sub0hm tank.
With that said, there is a line to fill, and don't go over that line (it's tempting sometimes) as it can cause leakage, annoyance, and other issues, like juice getting between the glass tank and the metal sleeve, and just all around yuckkiness.
If you like the N2, you will have the opportunity to upgrade to a 3 ml kabuki (or alternately, a clone, if you prefer to not spend that on a tank, though I feel it is worth it) to me the 3 ml makes a big difference.... It uses the same Nautilus coils. With that said, I still love my N2s and still use at least one every day... for flavor switchups. It's a fun little tank and the draw on it is pretty excellent, really well designed for MTL.
Anna