Could be the coolfire. 2000mah isn't really a lot, even for that kind of drain. You should see 'bout half-a-day of moderate vaping from it though... ...possibly much more than that at 25w and under. The common consesus seems to be that the battery lfe is great, but I doubt that the people saying this are running big-ass 24g coils in an rda.
What wattage are you running these coils at? The coils you're building are pretty large and require a lot power. Try building something smaller... ...right up against the minimum resistance. You'll be able to fire it better at lower power levels. One thing that's important to know about these regulated devices is that resistance doesn't affect battery life. The drain on the battery is determined by the wattage. The coolfire will pull as much current from the batteries as it needs to generate the set wattage. After that, it will swap out volts and amps to power the coil at that wattage. At the end of the day, 40w is 40w. 40w to a .2 ohm coil will require as much current from the battery as 40w to a .7 ohm coil would.
You will probably see considerably better lifespan from a dual 18650 regulated mod. That, or at least get yourself 60-75w single 18650 so you can swap batteries as needed.
Whatever it is, its not going to be the atty, though I will say that the Mutation X v4 definitely favors power hungry builds. When I use it on my mech, I carry four Samsung 25r's with me, though when I run it at 70-75w on my Sigelei 150, I tend not to bring any. That coolfire is great for tanks, especially for your MTL, non-sub-ohm stuff, but for an RDA... ...eh, you're getting closer to the top of its operational range just by the nature of the builds that suit them. Might want to look into something more power-efficient for that rda.
