Here is the process of degradation I experienced with all of my coils: At the beginning, the flavor is strong and smooth, I taste the sweeteners on my tongue very much, the airflow is perfect, and I can vape at maximum wattage (indicated on the coil) without any throat irritation (I don't vape at the max wattage except for a few hits). As time passes, the taste starts to get weaker and less sweet, airflow becomes less, and
vaping at max wattage would hurt my throat. I will need to lower the wattage from 30w to 25w, and after a while even 25w will hurt my throat. It seems dry hit is not binary, but instead a spectrum. The ability of wicks to absorb the juice fast enough decreases continuously. Throat irritation at 25w is when I decide I need to change the coil. (At this stage if I try 35w I will get that hellish dry hit.)