I agree with bigsmke. Dual cartos are not what they are made out to be. I started out using them in my
tanks and was wondering why I was often getting burnt taste with them. I gave single coil carts a try, and found out that I preferred them. Same vapor and vapor, but no more burnt taste, and I got longer battery use with them.

click image to enlarge it.
I have a theory: Dual coils are the same physically, except a dual coil cart will have a second heating coil half way up the carto tube above the bottom one. Looking at the arrows in the above diagram, when you suck on the carto, juice is sucked downward toward the bottom of the carto where the bottom heating coil is. Before long, the top and even the middle part of the polyfill is going to become dry. This can allow the top coil to dry burn the polyfil around it, resulting in that burnt taste I was always getting. So, unless you want to continuously "top off" your dual coil cart, the single cartomizer is your best bet.