I mix medicine flower vanilla for my wife. Amzingly i constantly get five weeks out of a 1.8 ohm nautilus coil. Even then it is still fine, i just do not want to push my luck. 9 watts and around 5 ml a day. So around 175 ml per coil. This has been consistent for 18 months, never a problem. I put it down to no sweetners and i always soak her coils in 50/50 unflavored for a couple of hours first.
That must be a very clean Vanilla to get about 175ml on each pre-made coil. Whatever you are doing seems to be working Dubminer, ConGrats.