There's no point in trying to clean a filler based carto unless you do it thoroughly. Thick gunk at the bottom is a byproduct of atomizing liquids that aren't totally clear, and must be removed. I always start with an alcohol (vodka for me) soak to dissolve remaining juice and gunk. Until alcohol comes out clear when I blow through the open end, it's not cleaned. I use very hot water to rinse, spin/thermometer shake or blow and set them battery-end down on light bulbs for 15min to completely dry. Except for damage to the center tube/hole, most have withstood multiple cleanings without a problem, white and fluffy.
The key is letting alcohol dissolve the gunk. I don't think water can do this as effectively and boiling can shrink some fillers.
I think cleaning isn't for everybody; those who use thick dark juices will have to clean more often with limited success, and those without patience to thoroughly do it shouldn't waste their time. Those who like to tinker, and I guess I'm one, get satisfaction from reviving them in a few minutes.
The key is letting alcohol dissolve the gunk. I don't think water can do this as effectively and boiling can shrink some fillers.
I think cleaning isn't for everybody; those who use thick dark juices will have to clean more often with limited success, and those without patience to thoroughly do it shouldn't waste their time. Those who like to tinker, and I guess I'm one, get satisfaction from reviving them in a few minutes.