eliquid mixture

So, i'm vaping on a nautilus 2 tank. So far i've used a 1.8ohm coil and a 0.7ohm coil, in 4 days. I've read people who use them for 2 week, yet i only got those 2 (which where included with the tank) to last 2 days each. Maybe i'm doing something wrong? The 1.8 ohm coil i vaped at 12.5w. The 0.7...