I use the method above for a quick rinse, but if I want to do a thorough cleaning, like if they've been used a few times or if I'm changing flavors. Many I've had have lasted for 2 months so far and still going strong. I keep a glass half full of vodka on my sink and if I get a bad taste or am done with a carto I just drop it in and let it soak, sometimes several days. When maybe 5 or 10 have built up I rinse them under hot water and blow the excess water out through the bottom (battery end), maybe 3-4 times. I then let them sit over night to completely dry, then you have completely clean cartos to refill, most will take 30+ drops and work all day, then I just repeat. In two months I've only thrown out 3, 2 would no longer give any vapor, I think the hair-like filament that heats up had broken, and the last one I overheated, the fill got so shriveled, brown and melted it would no longer take liquid, plus it tasted bad.
I know many will consider this a bit too much, but on a tight budget this has saved me a lot of money.
Just two last things, I top them off frequently to keep them from getting burnt, the obviously brown burnt cotton you might see looking down into the carto. And last, I tried to find the thread that explains it, but I use the centrifugal method to refill. Basically, fill the carto, put the caps on, put it into a battery bag and swing in a circle to force the
juice to the bottom, then top off. This lets you pack a lot more juice into them.
Sorry to be long winded, heh, but it works for me.
Oops, now after writing that I wonder if you were referring to cartomizers or regular carts... my bad...