I've been very, very frustrated lately because some days, it seems that I cannot get a decent hit to save my life. I said nothing about it because I figured it was my technique that was the problem --that I wasn't doing it consistently. I did notice that I wasn't having the problem when I used the passthrough. Today, I was having a great day with it. For 8 hours I was on the same battery and same carto with perfect hits each and every time. I thought "wow! I finally have this down!". Then, when I needed a fresh carto I also got a fresh, fully charged battery because I don't like to use a battery until it completely dies. I screw on the carto and take a few hits. Very little vapor, absolutely no throat hit. So, I keep that up for about another 3 minutes, and conclude that maybe the carto is bad. I use another fresh carto. Same problem. So, I switch to my third charged battery. Same problem. By this time I'm about to start screaming, so I put the carto on the battery I've been using all day. Perfect. But now I can't figure out why I'm having trouble with the other two batteries. Then I start to wonder about the battery cut-offs, so I test the first battery, the one I've been using all day with no problems. 5 seconds or so before it cuts off. The other two batteries? 2-3 seconds before they cut off. So, I can only conclude that this is the problem. Now, my question is is this normal? What is the cut-off time supposed to be?