I've been looking for the "dependable" atty for awhile now. I had a 510 atty last me 1 1/2 months before it died and the other atty that came with the starter kit lasted another month. I was really beginning to wonder what all the atty fuss was about. Then I ordered 15 new attys from 3 separate vendors and found out the sad truth about attys.
10 of the dang things were either defunct out of the box or too weak to even consider using, of the 5 that did work, some lasted a week and one.... one atty out of 15, lasted 2 weeks.
This is obviously a worst case scenario but it still can, and does, happen. Since then I've ordered a Juice Box mod from Carlos. 10ml bottle that pumps onto his own homemade atty and holds an 18650 battery... can't get much better than that. His homemade attys also don't have a determined life span...since one has never died to date. His current atty is going on 6 months!