My understand is that for some reason the polyfill in tank cartos does remain white & dry looking - at the top of the carto. If it is wet at the top of the carto, chances are that it is saturated & gurling - like mine. If I could get mine looking dry, I'd be happy.
Having said that, when I fill my tank cartos I use a syringe to add ~1ml to juice into the carto, then add ~ drops to moisten the top of the carto. Then I take my 2-4 dry hits. Since doing this I don't burn cartos now. (and once I learn not to suck too hard, maybe I'll stop ruining them by saturating them )