you know I suppose the cotton wicks can last for quite a while, I have heard people keeping them in for a week. I, on the other hand change them every time I refill, which for me is every other day, this is because I also vape a reo device as well as the kay-lite. its not that they need to be changed, its just that I keep doing different things to it, and changing to different juices. maybe once or twice I have just refilled without changing the wick, which worked fine. all I do, which im sure is no different to what you do is, turn device upside down, remove screw, syringe all the juice out(if switching flavors) and while the device is still upside down syringe the new juice in, I then replace the screw, turn right side up, mount to mod, and then take the primer dry vapes, let sit for a second and good to go. before refilling how low do you run the juice levels? maybe it is possible that the juice level gets to a point where there is insufficient pressure to keep the wick wet, it then gets slightly singed and is never 100 percent again? I have been using the micro coils in the reo for a while, but only for a short time in the k-lite, the devices are totally different so I am still learning the differences on how these micro's react in the k-lite. when I fill up the k-lite, as long as I can tilt it slightly and see an air bubble it seems to be good. I do fill it way over the plastic part, but not 100 percent full. with my syringe, I use the ml markings and just over 4ml is perfect. like I said as long as there is an air bubble when tilted it has been working great.