Hi vertigull.

to ESF.
It has been my experience that when a cart starts to get dry, vapor production will drop and a more harsh often hotter taste will occur. Just be especially careful with this when using a cartomizer, these were made and intended to be one time use disposable atomizers. Though they can be refilled and used more than once. If they are allowed to run dry, they may start to burn the filler. I have never tried one of these cartomizers, but I have seen pictures of ones that this was allowed to happen.
Refilling the cartomizers is not an easy a task as it is with conventional atomizer carts. so I would suggest carrying extra prefilled carts with you, and change them out when you first suspect it may be getting low.
Others have also suggested, leaving them sit standing up over night after refilling, to allow the liquid to fully saturate. And always drip your liquid down the sides and not down the middle when refilling. You can also refill these by dripping the liquid down through the battery connector end. And try not to over fill them. Like I said, I have never tried one of these types, but I would think, and others may correct me on this, using a syringe to refill may speed up the process.