Just got my first order of ikenvape cartos in. Platinum xl slotted. I primed per the baditude method filled my tank and vaped. Great flavor and vapor production. My question is whether the filler material should stay saturated.
Concerning your question, it depends upon if you are determining if the filler is saturated by looking at it after you have begun vaping for several minutes. If you look at the above diagram of a cut away punched cartomizer, you can understand how a cartotank works via negative pressure.
As you vape, juice is pulled both from the tank and the entire filler within the carto. Notice the red arrows in the diagram representing the juice flow from both. Within the carto, the juice level will fall, even if juice is also entering from the lower punched holes from the tank. It is normal for the top filler to look dry quickly after vaping a fully primed carto, but the filler will remain fully saturated where it most counts - around the heating coil.
In summation, don't expect the juice coming from the tank to keep the top filler wet; to do so would flood the cartomizer. The top will look dry, that's normal. The bottom half of the carto's filler (surrounding the heating coil) should stay saturated by the juice coming from the tank.
If you so desire, you can top off the carto when you do tank refills, but I myself rarely need to. A carto that is wicking juice well in a cartotank shouldn't need topping off.