I like them. A few tips: after filling, blow on it, and mop up the juice that collects on the contact. I have one dedicated to each flavor, and refill as needed. The only one that got clogged was Madagascar Vanilla. I rehabilitated it by soaking in vodka, washing in running water, fill with water, and blow until it is empty, to clean the wick. Give it another soak in vodka, dry, and she is ready to go. I don't know which part of this ritual are essential, and which are superstitious, but changing flavors is not a problem. How many cleanings it will endure is also a question.
I refill all of mine at a time, so the letting it sit may have something to do with my good luck.