Yup, I just posted about this in another topic. All of my newer Kangertech coils that have the 4 holes grow whiskers in actually a very short period of time, in fact they grow whisker faster than I do.
I don't understand the whole vacuum thing with regards to this, I thought the vacuum goes the opposite way, where the liquid is sucked into the coil head itself so that is going against the direction that the coil heads grow these whiskers.
Not sure how long they last after they start to exhibit this, as I'm not overly sensitive to the flavor or vapor, so I can use a coil for many many ml of liquid before I usually just replace them because I have a new one laying around. Can't say that I've ever experienced it where it's adversely affected the vape flavor or cloud production. But I've never seen one that gets really fuzzy with whiskers, usually it's just a few strands sticking out a good 1/4" or more through probably 2 of the holes.