Last time I checked, it was only spare batteries that had to be in carry-on. Batteries in devices are allowed in checked baggage. OTOH, I wouldn't want a phone, mp3 player, tablet or camera in checked baggage for other reasons. And I'm not sure whether a mod or eGo device counts as a device with batteries in.
The one time I had something suspicious* in my baggage the whole party's luggage was held up for 24 hours and my bag got to me four weeks later. But that was decades ago; it may have improved recently. I would still prefer to have everything they might want to ask questions about in my carry-on. If you're carrying a holiday's worth of eliquid, some of it will probably have to be checked-in because any in carry-on needs to be in the plaggy bag with your toiletries.
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* It was a birthday present for my sister -- a soapstone statue of Gnesha, wrapped insanely well and taped up into a 5 1/4" floppy disk box to protect it against light fingers and heavy handling. Mea-culpa; lesson learned.