The lifespan of a cartomizer, regardless of brand or style, is going to vary from one unit to the next. I have some that have been crap after the first fill, while others have stayed strong through a couple dozen refills. I use all KR808 gear (plus Go-Go batteries with KR808 adapters) and my preferred cartomizers are Boge LR, SmokTek LR, V2, and Bloog - all blanks. I fill with 80% - 100% VG juice, usually Copper Creek House Blend, Boba's, and Raf-a-Licious. Note, those are all high-VG and dark juices, which are known to shorten cartomizer life.
In the end, lifespan varies from one unit to the next. I find that typical expected lifespan for my usage to be about 5 - 10 refills. Keeping two or three in rotation all the time, I discard about one cartomizer a week.