I agree with you there, Kent. I also think that comes heavily into play with why I have been so 'lucky' as to have gone through well over 100 cartos - with multiple refills and wash cycles - and have only found charred material on a few of my very early units. I knew I had overused those, it was part of the learning process for me. Since then, I always have multiples in rotation (because of the 'every other drag' situation you mention). By giving them plenty of time to 'rest' between drags I'd wager that liquid saturation has definitely been my friend.
As an example, you can see earlier in this thread the pictures I posted while performing Scott's combustion experiment. That carto looked fresh as a daisy inside, and had been used quite a bit.
Yep. "Refilling" cartos like you refill a cart is simply not the way to do it with cartos. Like you say - have 'multiples in rotation' - because once refilled they really do need the time to thoroughly soak (preferably overnight - like most suggest) and anything other the horizontal after refilling is disastrous. I suppose you could top off with 8 or 10 drops but then that totally defeats the supposed advantage.
I use cartos only on 5 volt - the only way for me to get decent vapor from them, and so my experience with the charring - the "autopsies" are likely different from yours.