I just purchased a "genuine" 5 pack of Kanger 2.5ohm heating coils last night for $6.88 on eBay, in hopes of getting at the very least, quality control within the same blister pack of coils.
The ones I currently get, some lasts 2-3 days, some 2-3 weeks, however I do clean them after a week (if they last). I take them apart, remove the flavor wick, run a trickle of hot water over the coil for 2-3 minutes & allow to air dry for 2 days. Then after burning it off a bit, place a wick on it, along with a drop of e-juice, replace the stem & gasket, they're good to go for a while longer.
Unfortunately, I have issues with my hands, part of my disability cause, otherwise I'd totally rebuild my own coils & really save. I was told that the proper gauge camping wire & wick are all that's needed.
Speaking of TOS, with some of the stores, it would be obvious to anyone what's being sold. I'm glad that I didn't get the "debranded" 2 pack of Pro Tanks for $14 now, as it looked too good to be true. The one day shipping from Hawaii to North Carolina would cost that alone. I've been an eBay buyer since early 2009 & have learned that if a deal, regardless of the product, looks too good to be true, it normally is.
Cat