My last coil lasted 6+ weeks, ~70ml of juice. It was 5 wraps running @2.8 ohm being used on my Darwin @ 5.9 watts, until the last week or two, when I bumped it up to 6.4 watts.
Al
Six weeks is great but are you getting any vaper at 5.9 watts, at 2.8 ohms thats 4v, in other words a basic original batt/atty configuration, your darwin isn't doing anything. IME real vapor starts above 10 watts, enough to blow multiple 0 rings, but you also burn up more coils and much more juice, it is all relative, as in analogs some smoked filter less Camel and others Marlboro lights.
I'm sure they won't last long.