No matter how good you are at cleaning your coils, over time, the microscopic spaces that carry the e-liquid to the wick are going to get filled with residue. The longer you vape with it, the more gunk will accumulate, until it gets to the point where its wicking ability will be reduced to a fraction of its original performance.
You can postpone the inevitable by proper cleaning, but unless you can get in between the fibers and clean the crud out, it's gonna happen eventually.
You can postpone the inevitable by proper cleaning, but unless you can get in between the fibers and clean the crud out, it's gonna happen eventually.