I started with Bloog MF cartos just over a year ago, and since have used Bloog, Halo G6, SI Volt, Kanger horizontal-coil...basically most of the horizontal-coil design 808 cartos available.
OP, something is wrong if you're having trouble with that many cartos. I mostly buy blanks, and while I've had the occasional dud (maybe three in more than a year), the vast majority of them vape very well. The pre-filled cartos are identical to the blanks from Volt -- I've had both. Most measure 2.5-2.8 ohm.
Now I have a Provari, and with an adapter they still vape very well, up to 3.9-4V depending on the carto. I think I prefer Boge cartos now, but they are a lot noisier than 808 horizontal-coil cartos and aren't vastly superior, IMO.
I fill these blanks with 30-35 drops to begin with, dripping on the filler at an angle to avoid the center tube. I do not let them sit more than 5-10 minutes. The filler soaks up juice very quickly (I'm using Halo Tribeca in most cases) and they vape fine for hours. I've seen them last as long as a week or more before production lessens and I toss them.