Well, honestly, I've been alternating between about 10 different carts. I've taken the cores out and washed them in warm water a few times, but I can tell they are getting beat up a bit. I'm ordering a bunch of blanks tomorrow, and I have the JC starter kit coming, because for the price, it's a decent value and will keep me in juice and supplies for a while, I imagine. Still, even with the excessive use I've put these carts/cores through, they are still wicking and performing pretty darn well.
I am also getting another penstyle kit tomorrow, just because I want the extra charger and batteries, and that'll give me 3 atomizers and 4 batteries to work with, as well as a couple extra carts. I looked, and really, PS's starter kits are a great deal for the price, overall. I imagine from there I'll only have to buy a battery or atomizer every few weeks/months. I'm having great luck (knock on wood) with my entire kit as it is, and therefore I've decided to stick with my pen for the forseeable future.
But again, thanks for the info. I'll try and note what flavors I'm using and see if I can't come up with something a little more concrete regarding the browning (it's not burnt, btw, just 'juicy brown').