What they meant was some liquids can kill a coil in a matter of hours - like tar... It's usually the darker colored liquids. The darker they are the bigger the problem. You can tell when you get to the first part of cleaning: taking the thing apart.
After you unscrew the base the vent tube is exposed, with a silicone "cap" at the base of it. Move that cap up a bit on the tube so you can see what you are doing. Get a firm grip on the metal vent tube and wiggle and pull until it comes off. You can now see the wick and coil from where you removed that tube. If it looks like black tar covering the wick and coil your liquid is an atty killer. Let us know what you find.
See the video billbeckusa posted for how to proceed with cleaning.
Yes, my wicks are brown. The liquid I use turns brown after a while. I understand what you mean by it looks like tar. The liquid I use is not clear, it's called Cuba, a cigar flavored liquid. Liberty Flights has one called Churchill, which is clear. I used that in the past, and my new supply should arrive tomorrow. I just reordered the Churchill. It too is a PG liquid. I am so appreciative for you and everyone else taking the time to explain. When I originally got into this, I went to the local shop. They just taught me to put the thing together, took me a while to figure out what is what. I ended up with the Vamo based on all the great advice I have received on this forum. Now I have a better understanding on what I have to do.