So just to make sure I understand, the EMDC cartos will cause an early demise to regular eGo
batteries?
No. - The reason LR is not recommended for joye eGo batteries has to do mostly with LR single coil attys. When the coil goes out in an atty, there is often a sudden drop in ohms which causes a surge. The two most likely failure points in the eGo circuitry are the mofset and the resistor right before the mofset. The mofset is very sensitive to surges and that resistor isn't very durable.
So, a single low resistance coil vs two high ohm
coils in the same device is what it comes down to. It's tough to blow a 3.2 ohm coil with a ~3.4v device. If you do blow a coil with a dual coil, there is no sudden drop in ohms. As the coil fails, there is an increase in ohms instead because you're left with a single 3.2 ohm coil. --> With a single coil LR atty, it's quite common to blow a coil even at a voltage as low as ~3.4v. When that single coil fails, there is nothing else in the circuit...
Any LR circuit does have a higher amp draw, does drain the battery faster, and does generate more heat vs a standard resistance. I have seen absolutely no evidence that the joye eGo can't handle the amp draw or the little bit of extra heat from using dual coil cartos or LR cartos/attys. The only thing left is draining the battery faster. Well, sure enough. Draining the battery faster means having to charge it more often. The higher frequency of charge cycles, the less time it will last. How many extra charge cycles will you need in a month with an LR circuit vs a standard resistance? Perhaps 5 or 6. An extra half dozen charge cycles per month for a device rated for over 350 charge cycles isn't going to shorten its useful life very much.
To answer your question about single coil eGo-specific cartos: They existed long before the dual coils came out but smoketech doesn't make them. There are some single coil joye cartos that have the same skirt around around the connector that makes them only useful for eGo and eGo-style batteries (or other PVs using a 510 to eGo adapter). Those cartos work pretty well, but are a hassle to fill. I bought some from Cignot a few months ago and I think I've seen them a couple of other places.