There seems to be some confusion with dual coil resistance and the eGo style
batteries. Many people regularly use LR attys and such with no problems whatsoever. Others have obviously fried their batteries with them. Enough so that some vendors post a warning about not using attys or cartos of any kind below 2.0 ohms TOTAL resistance. The reason being that the device actually supplying power to the carto is a MOSFET (Metal Oxide Substrate Field Effect Transistor for those who care). This is an electronic switch that does the heavy lifting. The little button you push and makes a clicky sound is just a mechanical, momentary tactile(tact) switch that turns the MOSFET on and off. Tact switches will never handle the high 1.15 Amp current that even a 3.2 ohm carto would draw. Now, it doesn't care if you have a dual coil carto with two 3.2 ohm elements in parallel (which equals 1.6 ohms to the battery) or a single 1.5 ohm LR element. The current draw the Mosfet has to handle is still approx. 2.4 amps and that is the important thing. A 2.0 ohm element will draw 1.85 Amps and this seems to be the lowest recommended resistance by the manufacturers. Higher resistance equals lower current draw and that equals a happier MOSFET. BTW, a 3.2 ohm element draws only 1.15 Amps.
So, why do some survive and others don't? Many factors can conspire to affect longevity. A big one is that electronic devices like a MOSFET have Maximum allowable ratings plus a little for wiggle room. Wiggle room is my term for an undefined area where a device will operate above the MAX rating and not blow up. This will vary from device to device and it amounts to the luck of the draw which one has a lot of wigglage and which ones don't. Suppose a MOSFET has a MAX rating of 1.9 amps at a particular voltage - say 4 volts. you attach your 1.5 ohm carto to it and its as happy as a clam so you might presume that your device is blessed with a MOSFET with a lot of wigglage. BUT you also tend to take a few, short duration pulls on your PV and then set it down for awhile. That same setup in the hands of someone who takes 10 second pulls and chain vapes all day might fry the device in a few hours - The MOSFET overheats and burns out. Another device might fry immediately when you attach a 1-1.5 ohm carto regardless of your technique. That is wiggle room. Finally, different battery manufacturers may use devices from multiple sources so that will contribute to variations in the undefined region of wiggle room.
I deliberately did not mention wattage, whether some batteries may be built with higher-rated MOSFETS or other factors to keep a somewhat technical subject more manageable. So, A dual coil carto is really an LR carto in disguise.
Hope this helps.
