I don't use dual coils so I don't know how long they last. I use single coil 1ml cartos like Boge. How long they last depends on how well you keep them damp and how clear and thin your liquid is (mainly on how clear). It also depends on how much you vape. I use thin juices around 80PG/20VG that are light and totally clear or nearly clear. I can run about 15-20ml through a carto before it tastes/acts like I deserve a new one. For me that is 7-10 days. But since I alternate
vaping 2 models, each with a carto, it's 2-3 weeks.
Cartos are not much better tasting/
vaping than a new atomizer. However since you get to start a new cartomizer every week or so, it's like your setup is brand new over and over, where the atomizer just degrades and starts tasting/working less well. Cartomizers, once you learn to fill and settle and keep them damp, provide a more consistent
vaping experience for most.