I haunted the Sigelei thread for a good while, when I was shopping for my next mod, learning about the Sigelei, and then after I first got it, and one of the "regulars" therein is JeremyR, whom I quizzed unmercifully regarding battery safety -- AFTER reading the article about them in the ECF library. So I bought eFest Hi-Drain batteries, rather that something that costs less and *appears* to offer greater mAh, because I'd really rather be safe than save a few cents or even a few dollars, and my husband (the breadwinner!) agrees with me completely. I keep my two pairs of '350s in their proper pairs, because one set is flat, the other is button, and they are both always charged together and always used together; they are "rested" after charging, usually for about 24 hrs, and I check the voltage of them when I first insert them, throughout their life cycle, and make sure to remove and charge them before they get to "LOW VOL" on the Sigelei's display -- and never ever charge unattended. My face is 53 yrs old and shows it terribly, but I'd still rather keep it where it is, than splattered over the wall, and we just bought this house 2.5 yrs ago, the first one we've EVER bought, so I'm quite fond of it and have no desire to even risk burning it down. Oh, and I have no desire and no intention of EVER sub-ohming, in fact I don't go below 1.5 ohms as it's just too hot for me.
But you just cannot beat the longevity of stacked '350s. I can get 2 or 2 and half days out of them, used that way, and that is just... liberating!
Andria