Sounds to me like you are looking for a 401. Best battery life for a super mini, autoswitch so you can go hands free and small enough to 'hang'. Although I do have to hang it in my teeth. I don't think any e-cig can hang on your lip the way you are used to but the 401 is pretty comfortable balanced in your teeth and you can hold it n your lips long enough to get a drag. The cart life is bad but most 401 users dip the exposed atomizer right in the liquid which I find is about 1 analogues worth. I would recommend either going to ruyandirect.com if you want to order from china or myfreedomsmokes in the US. Go to his forum in the suppliers area and get the code for wholesale pricing.
The 401 is a good ciggie , but i wouldn't recommend as a first purchase. Carts are small and fiddly to refill, a 901 is easier to use overall and parts are readily available.
After reading and taking a lot of advice on this forum, I started with (and still love) my M401 - but more than that, I would specifically recommend the intellicig Evolution.
For me, it provides the perfect all-round balance of battery life, throat hit, round-end, nice size (bigger than a ciggie, but not huge... but, importantly for me, not wider) and flavour.
I will agree that the carts are more fiddly than some others, but I read and watched the videos before it arrived and soon found my own best way of doing things. I have actually counted the 'puffs' from a cart and from a home-filled cart I get around 80+ fairly deep draws from it, so I wouldn't say that the cart life is too bad personally.
I know that generally people don't recommend it as a 'starter' ciggie, but, for me, it was (and is) the perfect one.
(PS The 510 is not for me as I don't particulrly like the manual switch and it loses flavour compared to the M401, plus it has a greater diameter and so I don't find it that comfortable in my mouth. I haven't tried the 901, but I don't like flat mouthpieces, so again, that's not for me)