One problem I keep coming across is vapor/vacuum lock. I have yet to use a tank continuously and have it go past 2 months without getting the vacuum lock issue. This has happened on 4 different tank models and in a couple cases it happened on multiple tanks of the same model. It's always the same, I try a tank, love it, use it a bunch and then within 2-8 weeks it will start dry hitting (even with fresh coils) and it gets to were I have to loosen the cap after every two vapes (and of course 5-8 air bubbles will come rolling out of the wicking slots). It's worth noting that I generally run the wattage about half way between the low/high recommended wattage of the manufacturer (so I'm not abusing the coils). Also, I'm using either a 70 or 80 vg juice. The tank/coils will work great for several weeks and then the problem comes along and it doesn't go away. Either I'm doing something terribly wrong or I just have really bad luck. I'd love to know how long some of you folks have gotten your tanks to last. When you're done with it, what is it that made you believe the tank was done? The one thing I have yet to do is replace any of the seals on my top caps. Perhaps that will work and bring the tank back to like new performance. However, you generally only get one replacement and it would seem like that's bound to fail just like the original seal and I'm still going to be lucky to get the tank to last 3-4 months. Just gets frustrating rolling thru tanks so often. Apologies for the long post.