I too only get a day or too out of cartos. I've read where some people get 2 weeks
I have to say I am a pretty new vapor and even newer with using cartos. I started with the EGO tank system
before I dicovered theat cartos just taste WAY better. Yes I have noticed my cartos only lasting 2 days but I thought that it was with all juices not just KBV. Although I do have to say that 90% of the juices I vape are KBV's juices so I can't be sure, the other 10% I vape from other company's only last 2 days too though.
I'm not sure if it's mostly just bakery or sweet flavors but it seems like I can go a bit longer with tobacco flavors. Unfortunately I mostly only vape sweet flavors.
I just starting accepting that it's the price I'm going to have to pay for vaping. One more suggestion you might want to try the new Stardusts.
I've only had them for a short time but they seem to be very good and will definitely save you money. I still think I prefer my Boge cartos a bit more but the Stardust is VERY close and the best CE2 I've tried. Every other CE2 before I have hated. They're only about $6 so it's definitely worth a try if you are looking to save money.