Hi Olvis
I know you already contacted support regarding the matter, but I just thought I'd add my thoughts to the thread. The V3 carts shouldn't leak, the only time I have ever encountered a leak on them is when I'm using the device a hell of a lot and pretty much going at constantly, taking drag after drag, eventually you'll get a bit of build up on the bung of condensated eliquid, which you're right, does not taste nice. This also happens if your vaping techniques involves a lot of quick short sharp drags, they do not give the atomiser time to work properly. You want to be taking long slow consistent drags of around 3-5 secs, the vapour should almost fall into your mouth. The battery switch is very good and it'll activate with the lightest draw, and forcing it results in lower throat hit and vapour production.
The mouth ulcers could well be from the PG, although these are associated with the side effects of giving up normal smokes as well. Our PG liquid, which is in the carts, is an 80/20 PG/VG mix, our VG stuff is the reverse, so it may be enough to switch to the VG, again support will sort you out with this.
Our carts are as large as 35mm carts get, I know a lot of companies advertise 20, 30 or even 40 cigarettes a cart, this simply isn't possible from any technology I currently know of in a 35mm cart. In terms of puffs or inhales, you will get around 8-10 cigarettes worth depending on how you smoke, basically a full cart will provide between 110-120 inhales of around 3 secs. I'd bet my life that the 10 motives 35mm carts do not hold more than our carts, and hands down it should out preform them. If you got 8 days from a 10 motives, you were using it a lot less, either that or you've got a duff pack, we occasionally get a dud cart or 2 in packs, but it's not prevalent and a whole pack is very, very unusual. However if you are getting the same performance on refilling, then a cart misfill in production is not the issue.
Anyway, as I said, I know you've contacted support and hopefully we'll be able get this sorted out for you.