The point of the filler is to hold a lot of liquid. The liquid right next to the atomizer in the middle wets the "sock" which has the liquid that actually gets vaporized. With the filler in, you can
vape most of the liquid in a carto before refilling (close to one ml.) Without the filler, it's a lot more like dripping. You need to refill a lot.
Unless you have an automatic battery, don't worry too much about flooding. You can just blow it out of the center. BTW, if you take the filler out, a cartomizer is more prone to flood.
Another thing to consider is that you will break the wires on a certain number of cartos while removing the filler, rendering them useless.
I believe Dogsbody, who invented the condom method, was the person who came up with this. If you search the forum for him, you should find his videos and the discussion. When I last looked (a while ago), it seemed the consensus was "use the filler until it gets nasty and unwashable. Then remove the filler and see if you can get a little extra life out of it."