I have been using the Seego V-hit B for 18 months. I have burned out a dozen or so of their coils. For the first year I spent a lot of time trying to clean the heads, but found the carbon build-up could not be removed, even with an ultra-sonic ISO bath. I have settled on trying to use it at the lowest power setting to try to minimize carbon build-up, and they seem to last longer. I use a MOD with a power setting of 4 watts. Since the resistance of the coils varies, I let the MOD figure the correct voltage.