I have a kr808d1 too, and love the cartos from litecigusa, they are of superior quality to the two other cartos I've tried (V4L and V2Cigs). In my experience, the V4L premium (soft cap) cartos burn very quickly, no matter how saturated I keep them. I've also tried the cartos from V2cigs (hard caps), they're pretty good, but they burn inside as well and start to get clogged after a few refills with
juice.
Both the Low resistance and standard at litecigusa are great. The stuffing is dense, holds a good amount of
e-liquid, keep on working after many refills, and if you keep them nice and saturated, the wicking material seems to not burn at all.
I ordered some maxxfusion cartos from bloogplanet, haven't gotten them yet, but some other posters have recommended them, saying the wick is very burn resistant and long lasting. I'll have to report back on those when I get them.
Good luck!