To me these coils remind me of cartomizers. When the draw gets tight its usually time to replace them. I have done experiments where I vaped on them for different intervals of time and then took them apart to look at them.
Even after a week with a clear juice it just looks nasty! I just can't see myself
vaping on that. I like to rebuild my Protank coils. But even with regular Protank coils you can rinse them off and do a quick dryburn and they are nice and clean again.