I bought this one and am satisfied with it. For my cell phone thats is; I dont own a crafty. Twice the charge (and size I guess) for the same price.
http://www.merimobiles.com/xiaomi-5v-2a-10400mah-power-bank-for-smartphone-tablet_p/meri8548.htm
About long term battery usage. I usually vape alternating 2 solos (the persei is new). Fully charge one while I fully deplete the other. I killed my 2 solo battery pack in about 8 months ( I had about three 0.07g bowls per solo at that point). Since the batteries are similar in size, I see myself killing a crafty battery in 4 months..
Im curious to know how the usb powerbank performs while using it on a weak/dead battery. What is the point, if there is, where the crafty will NEED to be sent for battery replacement to work.
Out of my ass, I think the mighty will always be able to work while plugged even on a dead batterry, while the crafty will need a battery replacement here and there. Too bad we cant do it ourself..