a lot depends on where you vape at. I vape at max watt output that my devices are capable of. That is 15 watts. Some times more, if I take the kick out my mech mod to see if my current build is wicking well enough. Since the max on most devices is 15 watts, if you start out on say a 2.4 ohm coil, well the maximum I can vape is 6 volts on the Provari, giving me my desired 15 watts of output across the coil. Now with most coils, once it is used for a bit the ohms can drift up, and then I am vaping at on 12 or 13 watts. For that reason I like my builds to be .9 ohms to 1.4 ohms max. That way I can use them on my Provari or my kicked mech mod, with out a problem and be able to get some good life out of the build without losing my 15 watt threshold. Also if you are using a mech without a kick, or a non variable device, then you only have the voltage that is coming out of the battery producing the watts that the ohms of the coil puts out.
I find that the more watts you use the faster I go through batteries. Once I started using build that could wick enough juice at 15 watts, I could burn through 4 18490's in a day. I can also vaporize 12 to 15 ml of juice in a day too, more on my days off.
Like everything else in the world of vape, finding ones preferences, of ohms, watts, gauge of wire, nic level, VG/PT ratio, flavors, attys.... is a matter of trial and error, and always changing once you try different things and styles and builds and...
In my different rba's I have 4 different style of builds, once I think that I've found the best answer, I'll try something else that pops into my head. hmm, what if I combine a micro style build with a genesis style build with cotton, what would I get. Apparently a pretty dang good vape. But so is my Vertical mounted dual serial coil build with an external wick.