I've had originally bought a 5 pack of empty cartos from Volcano when I ordered my Inferno. I initially filled three with some JC liquid. Of those three, I am still using one, I tossed one because it seemed that it wasn't working at all since I was just sucking the juice back out of it no matter how long I held the button, and the third I tossed because it had a heavy burnt plastic type taste. The fourth carto I filled with a non-nic flavor, but barely use it. And the fifth I've just started using now. The funny thing is, of the five that I've filled, only one works in at a superior level. The other four were either mediocre, or have been trashed.
I did purchase a pack of 5 carto's from my local vape shop, but these have the polyfill in it, which I wasn't used to. They seem to work a lot better than the ones that I got from Volcano, but it seems that I am still trying to figure these things out.