Hi there, ive been using the .25 SS coils on my crown tank, on a 80/20 juice at round about 67 watts. ive been using the coil for about 5 days and it seems as if the coil is starting to near it end ( slight burnt taste and darkend cotton). i would like to know how long more or less are they suppose to last and or how i can increase their life expectancy ( provided it was correctly broken in and primed)