I am using them. I don't know how long they are supposed to last but they seem to lose their energy after about a week or so. I haven't really kept a log or anything.
They really sizzle and crack and pop the first few days and make great vapor and hold a lot of liquid. But then they seem to get dull and stop sizzling, harder draws, etc. I use VG only so not sure how much difference that makes - if I have to
buy a new one a week thats what I will do I guess, only $4 each (well + shipping...)