Other than some "cool" factor I am unclear as to why there is still so much discussion and grief about battery life... why use batteries at all? The "cord" of a USB attachment is a LITTLE less cool - but the small size and ease and SUPER long life of battery power packs make them my ultimate choice! I value reliability over cool. I am a heavy vaper, but I don't bother with charging or carrying around or buying batteries, nor do I run out of power (making my only "spare" issues the atty's). I use both the YP-M8565 Power Bank (lasts forever (full week or more!), used with my 801 mega smoke system) and the sleeker Kensington K38021/K33396 (my 401 power source (a little less longevity (5 days or so...), but more cool factor and fits in the smallest of pockets) - both of which provide EXCELLENT and constant power for all my ecigs. Seems to me that trying to find a longer lasting (and generally bigger) battery to keep up with and constantly recharge, and reconnect and such, is a bit like buying cartridges instead of juice to refill with - 
Now, when they make a watch battery or something similar that keeps on ticking without recharging very often (once a week or less?) with enough power for ecigs - I might change my method. But for where things are now - I'll keep my vape 'up and on" at all times when and where i want it with power banks!
it took me a great deal of time and research (mostly here on the forum) and trial and error (buying things i saw in the store that I thought might work!) to find the ones that really do work- and those 2 listed above WORK GREAT with all usb ecigs. just my 2 cents worth.

Now, when they make a watch battery or something similar that keeps on ticking without recharging very often (once a week or less?) with enough power for ecigs - I might change my method. But for where things are now - I'll keep my vape 'up and on" at all times when and where i want it with power banks!
it took me a great deal of time and research (mostly here on the forum) and trial and error (buying things i saw in the store that I thought might work!) to find the ones that really do work- and those 2 listed above WORK GREAT with all usb ecigs. just my 2 cents worth.