I agree with trog; 901s wear out. I was convinced after 3 weeks of vaping on a 901 that these 2-week prophets were full of bull, but then I ordered some new ones, and found that just because they're still producing vapor doesn't mean they're in top shape. I ordered my first ones from totally wicked, and they're still around 5 weeks later, but by no means producing like they were the first two weeks. I ordered some much lower priced ones from somewhere else, and guess what, they hit really hard for about a week and a half, then they still produce vapor, but the throat hit isn't there. I can deal with ordering new ones every two weeks if it means I get a better taste/throat hit/experience. That's just the truth of it. Still costs me less than analogs (and even if it didn't, it tastes a whole heck of a lot better).