Battery life - while there are many that claim to get 1-2 days out of a single 18650, I have to wonder how much juice they are actually going through. My Vamo V10 (VV/VW) with dual 18350's (serial config) that sits in the throne room lasts a few WEEKS. Then again, I don't spend all day/night sitting on the throne.

Realistically, the V10 and Kanger STM mounted with 1.3ohm Ti build @ 4.5V will last longer than a set of 18350 batteries.
I use ~4-8ml a day. My TC mods run @ 15-25W/J, 460F.
My Sig Vmax mini (single 18350) might last 2-4hrs, a telescoping Sig Vmax (18650) might last nearly 2x that - 6-8hrs as does all my single 18650 TC mods. (if I start on a freshly charged and full tank in the AM when I get up @ 7-8am I'll likely be swapping batteries or mods long before dinner time.
Here's where the dual 18650's really shine. An IPV4s or Boxer SX350 with LG HG2's can easily last from sun up to sun down and beyond (7am to 11pm) but may (or not!) have enough charge left over for a few draws/puffs/pulls the next morning. Here's where I'll pull the batteries and put them on the charger over night so they are fresh in the AM.
While I enjoy the way the SXminiM, IPV4s and Boxer-350J fit in the hand a YiHi mod with dual 18650 and similar form factor as the IPV4s is a sure thing buy in my book. (unless of course they REALLY fubared the thing, which is rather doubtful considering it is YiHi.)
I'm looking forward to further news of YiHi's latest chip and mod!