Well I've had a few different cartomizers and kits, CE5+, Vaporfi, Kangerteck Emow, and my current (and favorite) is the Aspire Nautilus Mini with the new organic cotton coils (bottom vertical coil) at 1.8 ohm. My first Nautilus Mini I got with the kit that had the CF battery, and its nice, but rather long battery and only 1000 mAhour, charge lasts about a day for me.
My second Nautilus Mini I bought with an Eleaf Istick 30W and I looooovvveee this battery, its really compact, but lasts over two days before charging, 2200 maHour. I HIGHLY recommend you buy the Silcone sleeve for the Eleaf, because it has a nice but slippery metal finish, and the sleeve gives you an excellent grip and doesn't cost much. I just bought my last Nautilus Mini, Eleaf Istick 30W Full KIT (has the charger, other stuff), Silocon Eleaf sleeve, and extra coils at WorldofVape:
Eleaf iStick 30W Full Kit - $29.95 - WORLDofVAPE
I'm looking now, and the Eleaf Istick 30W Full Kit is on sale at 29.95, thats the best I've seen, when I bought it last week it was 35.95, and still a good price then!
Good luck

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I just bought pretty much the same things! I started with disposables May 2014, then moved to a regular V2 Kit with long batteries and the refillables cartridges, so I have plenty of liquid. I really needed an upgrade! That seemed to be what was generally recommended here (Nautilus Mini and Eleaf Istick 2! Bought 2 of each to start and 5 extra coils! They just arrived in my hometown and should be delivered today! CHRISTMAS for me! LOL I ordered them from MVS.