I think that the cartos don't absorb new juice very well if they are completely dry. It's like a kitchen/bathroom sponge, when it's totally dried out, the water doesn't absorb as well as a damp sponge....water just runs off instead of absorbing. I get great results just blowing out as much water as possible after cleaning and then refill. I've been able to keep using the same cartos for a couple of months....great flavor and vapor. Some have had to go in the trash can, but not many.
And you haven't had any problem with water on your tongue when vaping after you refill them? I can't figure out any other reason for this problem I had than that the filler was still wet with water, and I was vaping the water, and it was ending up on my tongue -- and then into a kleenex. It was a real pain for about three days, having to spit into kleenexes all the time (but only when I was vaping those cartos I had cleaned that obviously hadn't completely dried out).
I like the thought of cartos being completely dry inside; then I can pretend they're brand new and ready to be filled for the first time.