I just replaced it and it works but thank you! How often do coils need to be replaced typically?
It's highly variable. First, the quality control isn't great. Second, it depends a lot on the juice you use. Thick, dark juices tend to clog them up quicker. Lastly, there's the question of whether or not you clean them.
With most juices, I tend to use them for a couple tankfuls, then toss the old ones into water to soak when I'm filling my tank at night. In the morning I rinse them pretty well, then toss them into some alcohol to soak while I'm away. Lastly, when I get home, I'll give them a rinse and let them soak in water again. With that process, I've only had one go bad in the seven weeks I've been using them. They do tend to produce less vapor with time but usually another rinse cycle cures that.