I use the Vivi Nova with an ego c-twist and a 2.4 head and 6mg liquid. I usually replace the heads once a week (i don't bother cleaning them). Sometimes, though, i get very hot painful hits on the back of my throat a day or so after replacing the head. Sometimes it takes less than a day. It always goes away when i change the head and when don't have this problem, i can go a week or more on a head just fine. So, i figure i'm getting some bad heads. I have ordered them from both Gotvapes and Aquavapor but i can't tell if the bad hits are happening from one particular purchase since i didn't bother to keep track of which heads i got from where. Has anyone else experienced this? Is there a particular website that you could recommend that i could good quality Vivi Nova heads from? Please don't waste your time telling me about recoiling them. It sounds interesting but i just don't have that kind of time or inclination. I'm a "throw it away and replace it" kind of guy.